Method for manufacturing ferroelectric thin film device, ink jet recording head, and ink jet printer

ABSTRACT

It is an object of the present invention to control the crystal orientation of a ferroelectric thin film as dictated by the application of a ferroelectric thin film device. To accomplished the stated object, a bottom electrode containing at least iridium is formed over a surface preparation layer whose main component is zirconium oxide, and an ultra-thin titanium layer is laminated over the bottom electrode. An amorphous layer containing the elemental metal and elemental oxygen that constitute the ferroelectric is formed over the titanium layer, and a crystallized ferroelectric thin film is formed by heat treating this amorphous layer. If the thickness of the titanium layer is kept between 2 nm and 10 nm in the lamination thereof, the ferroelectric thin film will have a priority orientation of (100), and if it is kept between 10 nm and 20 nm, the ferroelectric thin film will have a priority orientation of (111).

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to ferroelectric thin film devicethat functions as a piezoelectric device, a nonvolatile ferroelectricmemory device, a pyroelectric device, or the like, and more particularlyto a technique for controlling the orientation of a ferroelectric thinfilm, and to a technique for improving the bottom electrode of thisferroelectric thin film device.

[0003] 2. Description of the Related Art

[0004] Crystalline materials consisting of compound oxides that exhibitferroelectricity, such as lead titanate zirconate, barium titanate, andlithium niobate, have numerous functions, including spontaneouspolarization, a high dielectric constant, an electro-optical effect, apiezoelectric effect, and a pyroelectric effect, and as such are used inthe development of a wide range of devices. For instance, thepiezoelectric properties of these materials are utilized in capacitorsin FRAM (Ferroelectric Random Access Memory), DRAM (Dynamic RandomAccess Memory), and the like, their pyroelectric properties are utilizedin infrared linear array sensors, and their electro-optical effect isutilized in wave-guide type light modulators, so these materials can beused in many different fields. Ferroelectric thin film devices havingthese various functions are also called functional devices.

[0005] It is often the case with a ferroelectric thin film device suchas this that the characteristics vary with the crystal orientation ofthe ferroelectric thin film. For example, most lead titanate-basedferroelectrics, which are a type of ferroelectric having a perovskitetype crystal structure, have a tetragonal crystal structure, and havespontaneous polarization in the c axis direction. Accordingly,spontaneous polarization in the direction perpendicular to the substratecan be maximized by orienting the c axis to be perpendicular to thesubstrate (c axis orientation treatment), allowing the performance of aferroelectric thin film device in which this characteristic is utilizedto be utilized to full advantage.

[0006] For this reason, it is important to control the crystalorientation in the formation of a ferroelectric thin film, andparticularly a lead titanate-based ferroelectric film having aperovskite type crystal structure. Furthermore, since the electricalcharacteristics of these ferroelectric thin films vary with theorientation of the crystal plane, an orientation treatment must beperformed according to the intended application of the ferroelectricthin film device. For example, a (100) priority orientation is known tobe preferable with a nonvolatile ferroelectric memory device that makesuse of the polarization characteristics of a ferroelectric thin film,such as a FRAM. With a piezoelectric device that is utilized as anelectromechanical transducer (actuator), in the case of DC drive, a(111) priority orientation is known to be preferred because of thepiezoelectric constant d₃₁ characteristics in the drive voltage region.

[0007] Except in the case of natural orientation, the crystalorientation of a ferroelectric thin film is affected by the crystalorientation of the bottom electrode or substrate that serves as the basein the formation of the ferroelectric thin film. Accordingly, properselection of the material of the bottom electrode or substrate thatserves as the base is absolutely essential to controlling theorientation of a ferroelectric thin film. Generally, a silicon substrateis used as the substrate of a ferroelectric thin film, and a silicondioxide film is formed in order to ensure good electrical insulationbetween the bottom electrode and the substrate, so a requiredcharacteristic of the bottom electrode is that it have goodorientability even when formed on an amorphous film. Platinum electrodeshave been used in the past as electrodes that satisfy this requirement.The lattice constant of a platinum electrode is matched to that of leadtitanate zirconate, and because platinum is resistant to oxidation, noplatinum oxide layer is formed at the interface with the dielectriclayer, so the performance of the device tends not to deteriorate.

[0008] As to technology related to the bottom electrode, it has beenreported in Japanese Patent Laid-Open No. 07-245236 that a structurehaving an iridium layer or an alloy layer of platinum and iridium as thebottom electrode is favorable in terms of the matching of the latticeconstants of the bottom electrode and PZT. Japanese Patent Laid-Open No.08-335676 deals with an improvement on this technology, reporting thatif nuclei of a component element of PZT (titanium) are formed on thebottom electrode in a structure having an iridium layer or an alloylayer of platinum and iridium as the bottom electrode, crystals willgrow around the nuclei and good contact with the PZT film can beensured.

[0009] As to technology related to the substrate that serves as a base,it has been reported in Japanese Patent Laid-Open No. 5-281500 that alithium niobate thin film is formed by sol-gel method on a sapphire(001) plane monocrystalline substrate. According to this technique, theaxis of crystallization of a ferroelectric thin film can be uniaxiallyoriented by utilization of the crystallinity of the substrate.

[0010] However, even though it was possible to form a ferroelectric thinfilm with excellent orientability by optimizing the conditions thataffect the orientation of a ferroelectric thin film by means of thebottom electrode (or substrate), such as matching the lattice constantsof the bottom electrode (or substrate) and the ferroelectric thin film,as with the above-mentioned prior art, it was difficult to control theorientation of a ferroelectric thin film as desired according to theintended application of the ferroelectric thin film. For instance, if anattempt was made to vary the film formation conditions in the formationof a PZT film by sol-gel method, it was difficult to control the (100)priority orientation, which is favorable for a nonvolatile ferroelectricmemory device, and the (111) priority orientation, which is favorablefor the DC drive of an electromechanical transducer, as desired.

[0011] Also, diligent study by the inventors revealed that when aferroelectric thin film device is used as an electromechanicaltransducer, the piezoelectric constant d₃₁ will be higher if theferroelectric thin film is set to a priority orientation of (111) in adrive frequency band of just a few kHz (low frequency band), and thepiezoelectric constant d₃₁ will be higher if the ferroelectric thin filmis set to a priority orientation of (100) in a drive frequency band ofseveral dozen kHz (high frequency band). This seems to be because thepiezoelectric constant d₃₁ remains more or less constant regardless ofthe drive frequency if the ferroelectric thin film is set to a priorityorientation of (100), whereas the piezoelectric constant d₃₁ decreasesin value as the drive frequency goes up if the ferroelectric thin filmis set to a priority orientation of (111). It is therefore desirable tobe able to control as desired the orientation of a ferroelectric thinfilm according to the drive frequency of the electromechanicaltransducer.

[0012] Also, the technology disclosed in Japanese Patent Laid-Open No.08-335676 allows crystals to be grown around nuclei and good contactwith a PTZ film ensured by forming nuclei of a component element of PZT(titanium) on the bottom electrode, but if iridium alone was used as thebottom electrode and the PZT film was formed by sol-gel method, thenthere was a problem in that the bottom electrode took in oxygen andswelled in the course of the baking of the PZT film. Because the bottomelectrode became hard and brittle if it took in oxygen, the bottomelectrode would break if used as an actuator.

[0013] The structure that used to be employed when a ferroelectric thinfilm device was used as an electromechanical transducer had an adhesivelayer (buffer layer) of titanium, chromium, or the like provided betweenthe bottom electrode and the surface where this transducer was installedin order to enhance the adhesion between the electromechanicaltransducer and this installation surface. The inventors of the presentinvention, however, discovered that in the course of the manufacture ofan electromechanical transducer, the element that makes up the adhesivelayer, such as titanium, is diffused as a result of heat treatment andmoves into the ferroelectric thin film, which diminishes thepiezoelectric characteristics of the electromechanical transducer. Thereason for this seems to be that the titanium becomes admixed with theferroelectric thin film and disrupts the stoichiometric ratio in thisfilm, or produces a layer with a low dielectric constant at theinterface between the bottom electrode and the ferroelectric thin film.

[0014] A ferroelectric thin film has spontaneous polarization, andbecause the polarization direction can be inverted by the action of anexternal electrical field, this characteristic can be utilized tomanufacture a nonvolatile memory. When a ferroelectric thin film wasapplied as a memory device, an alloy of platinum and iridium, iridiumalone, or iridium oxide was used in the past as a bottom electrode forapplying an electrical field to the ferroelectric thin film in an effortto enhance the characteristics of the ferroelectric thin film andprevent their deterioration over time. Examples of such usage are foundin U.S. Pat. No. 5,191,510, Japanese Patent Laid-Open No. 07-245287, andelsewhere.

[0015] However, the bottom electrodes composed of an alloy of platinumand iridium, iridium alone, or iridium oxide that were used for memorydevices posed problems when used as electromechanical transducers, suchas in an ink jet recording head. Specifically, the electromechanicaltransducer must itself be deformed with an ink jet recording head, butwith a bottom electrode containing iridium, there were problems in thatthe bottom electrode was too hard and the film stress generated in thebottom electrode was too high. Another problem was poor adhesion betweenthe bottom electrode and the installation surface and between the bottomelectrode and the ferroelectric thin film.

[0016] Furthermore, the problem of markedly increased leakage currentwas encountered when iridium was used as the bottom electrode, asdiscussed in the article “Explanation of the Leakage Mechanism of a PZTCapacitor Deposited on an Ir Electrode (Lecture Summaries from the59^(th) Convention of the Applied Physics Society, issued Sep. 15, 1998,p. 450). Accordingly, the use of platinum is normally preferred for thebottom electrode when a ferroelectric thin film is used as an actuatorfor an ink jet recording head.

[0017] Platinum is therefore favorable for the bottom electrode of aelectromechanical transducer, but there has been a need for a bottomelectrode having a structure capable of preventing the admixture ofimpurities (such as titanium) into the ferroelectric thin film duringthe electromechanical transducer manufacturing process, and of enhancingthe adhesion between the bottom electrode and the installation surfaceand between the bottom electrode and the ferroelectric thin film.

[0018] When an alloy of platinum and iridium was used for the bottomelectrode of an electromechanical transducer as disclosed in JapanesePatent Laid-Open No. 07-245236, or when iridium oxide was used asdisclosed in Japanese Patent Laid-Open No. 07-245237, a problem wasencountered in that residual stress was generated in the bottomelectrode containing iridium in the course of baking and crystallizingthe ferroelectric thin film, and this residual stress diminished thecharacteristics of the electromechanical transducer. For example, theresidual stress generated in a bottom electrode could impart strain tothe ferroelectric thin film and undesirably lower the percentage ofvolumetric change.

[0019] In view of this, it is an object of the present invention toprovide a method for manufacturing a ferroelectric thin film device withwhich the crystal orientation of a ferroelectric thin film can becontrolled as dictated by the intended application of anelectromechanical transducer. It is a further object to provide an inkjet recording head whose ink discharge drive source is anelectromechanical transducer obtained by this manufacturing method, aswell as a method for manufacturing this head, and an ink jet printerthat makes use of the same. Another object of the present invention isto provide a nonvolatile ferroelectric memory device in which aferroelectric thin film device obtained by this manufacturing methodserves as a capacitor, and a method for manufacturing this memorydevice.

[0020] Yet another object of the present invention is to provide amethod for manufacturing an electromechanical transducer having veryreliable drive characteristics when iridium alone is used as thematerial for the bottom electrode.

[0021] Yet another object of the present invention is to provide anelectromechanical transducer with which adhesion with the installationsurface can be enhanced without diminishing the piezoelectriccharacteristics, and an ink jet recording head and an ink jet printerthat make use of this transducer. Another object of the presentinvention is to provide a method for manufacturing an electromechanicaltransducer having a layer structure with which adhesion with theinstallation surface can be maintained without diminishing thepiezoelectric characteristics.

[0022] Still another object of the present invention is to provide anelectromechanical transducer having good piezoelectric characteristicsas a result of reduced residual stress during baking, an ink jetrecording head and printer that make use of this electromechanicaltransducer, and a method for manufacturing an electromechanicaltransducer.

SUMMARY OF THE INVENTION

[0023] With the method of the present invention for manufacturing aferroelectric thin film device, a bottom electrode film containing atleast iridium is formed on a surface preparation layer whose maincomponent is zirconium oxide, and an ultra-thin titanium layer islaminated over this bottom electrode. Next, a crystallized ferroelectricthin film is formed by forming an amorphous layer containing elementalmetal and elemental oxygen that constitute a ferroelectric over thetitanium layer, and heat treating the amorphous layer. It was confirmedthat the orientation of the ferroelectric thin film can be controlled byadjusting the film thickness during the lamination of the titanium layerat this point. For instance, if the thickness of the titanium layer isat least 2 nm and less than 10 nm, the ferroelectric thin film will havea (100) priority orientation, and if this thickness is at least 10 nmand less than 20 nm, the ferroelectric thin film will have a (111)priority orientation.

[0024] Therefore, a ferroelectric thin film device that is favorable asa electromechanical transducer used with DC drive or low frequency drivewill be obtained by setting the thickness of the titanium layer to atleast 10 nm and less than 20 nm, whereas a ferroelectric thin filmdevice that is favorable as a capacitor for a nonvolatile ferroelectricmemory device, or an electromechanical transducer that is favorable forhigh frequency drive will be obtained by setting the thickness of thetitanium layer to at least 2 nm and less than 10 nm.

[0025] It is preferable for the ferroelectric thin film to be aferroelectric whose constituent components are at least titanium andlead, and lead titanate zirconate is particularly favorable. It ispreferable for the ferroelectric thin film to be formed by sol-gelmethod. A sol-gel method is preferred in terms of orientation controlbecause the crystallization of the ferroelectric thin film proceeds fromthe bottom electrode side.

[0026] It is also preferable for the bottom electrode to be a singlelayer of an iridium film or a laminate film having a laminated structurecomprising an (iridium layer)/(platinum layer), a (platinumlayer)/(iridium layer), or an (iridium layer)/(platinum layer)/(iridiumlayer), in that order starting at the surface preparation layer.

[0027] The ink jet recording head of the present invention comprises anelectromechanical transducer obtained by the manufacturing method of thepresent invention, a pressure chamber whose internal volume is varied bythe mechanical displacement of an electromechanical transducer, anddischarge outlets that communicate with the pressure chamber and fromwhich ink droplets are discharged. The ink jet printer of the presentinvention has a printing function comprising the ink jet recording headof the present invention.

[0028] In the method of the present invention for manufacturing an inkjet recording head, a surface preparation layer whose main component iszirconium oxide is formed on a silicon substrate surface, eitherdirectly or via a diaphragm film, and an electromechanical transducer isformed by the above-mentioned manufacturing method of the presentinvention over this surface preparation layer. The electromechanicaltransducer is then separated so as to line up with a position where themechanical displacement of the electromechanical transducer can beimparted to the pressure chamber.

[0029] In the method of the present invention for manufacturing anonvolatile ferroelectric memory device, there is a step formanufacturing the capacitor of a memory cell by the above-mentionedmanufacturing method of the present invention.

[0030] The method of the present invention for manufacturing anelectromechanical transducer comprises the steps of forming a bottomelectrode composed of iridium alone over a surface preparation layerwhose main component is zirconium oxide, laminating a titanium layerwhose film thickness is at least 15 nm and less than 30 nm over thisbottom electrode, and forming a crystallized ferroelectric thin film byforming an amorphous film containing the elemental metal and elementaloxygen that constitute the ferroelectric over said titanium layer andthen heat treating this amorphous film.

[0031] The oxygen content of the bottom electrode in the course ofbaking the ferroelectric thin film can be kept to a minimum and anelectromechanical transducer with excellent toughness can be provided byadjusting the thickness of the titanium layer laminated over the bottomelectrode to within a range of at least 15 nm and no more than 30 nm.

[0032] The priority orientation of the ferroelectric thin film can becontrolled to the (111) plane or the (110) plane by adjusting thethickness of the titanium layer to within the above range. The step offorming the ferroelectric thin film is preferably a sol-gel process orMOD process.

[0033] The electromechanical transducer of the present invention furthercomprises an adhesive layer formed from an alloy containing ananti-diffusion metal and formed between the bottom electrode and thesurface where the transducer is installed, and an anti-diffusion layerformed from an alloy containing the anti-diffusion metal and formedbetween the bottom electrode and said ferroelectric thin film.

[0034] The anti-diffusion metal is selected, for example, from the groupconsisting of iridium, palladium, rhodium, ruthenium, and osmium. Theabove-mentioned adhesive layer is, for example, an alloy of theanti-diffusion metal and the metal that constitutes the bottomelectrode. The above-mentioned anti-diffusion layer is, for example, analloy of the anti-diffusion metal and an adhesive metal that is eithertitanium or chronium. The bottom electrode is made of platinum.

[0035] It is preferable for the ferroelectric thin film to be formed ina thickness of at least 1 μm. The baking treatment must be repeatednumerous times for this thickness to be achieved, but the diffusion ofthe titanium or other adhesive metal is prevented by the anti-diffusionlayer of the present invention even though the baking treatment isperformed numerous times.

[0036] The ink jet recording head of the present invention isconstituted by an arrangement of the electromechanical transducers ofthe present invention on the diaphragm film that forms at least one sideof a pressure chamber filled with ink. The diaphragm film is, forexample, constituted by the lamination of a silicon oxide film with azirconium oxide film or the like. The ink jet printer of the presentinvention is a printer furnished with this ink jet recording head as anink discharge means.

[0037] The method of the present invention for manufacturing anelectromechanical transducer comprises the steps of forming an adhesivemetal layer composed of an adhesive metal over the surface where thetransducer is installed, forming a first anti-diffusion metal layercomposed of an anti-diffusion metal over the adhesive metal layer,forming the bottom electrode over the anti-diffusion metal layer,forming a second anti-diffusion metal layer composed of theanti-diffusion metal over the bottom electrode, and baking theferroelectric thin film while this ferroelectric thin film is formedover the second anti-diffusion metal layer, and thereby diffusing theadhesive metal all the way to the second anti-diffusion metal layer andproducing an anti-diffusion layer at the location of the secondanti-diffusion metal layer, promoting the alloying of the anti-diffusionmetal and the bottom electrode, and producing an adhesive layer at thelocation of the adhesive metal layer and first anti-diffusion metallayer.

[0038] Preferably, a metal selected from the group consisting ofiridium, palladium, rhodium, ruthenium, and osmium is used as theanti-diffusion metal. Also, either titanium or chronium is used as theadhesive metal.

[0039] The electromechanical transducer of the present inventioncomprises an interlayer formed from a compound selected from the groupconsisting of zirconium oxide, tantalum oxide, silicon nitride, andaluminum oxide and formed on the surface where the transducer isinstalled, and a bottom electrode formed over this interlayer. Thebottom electrode comprises a first layer composed of an alloy of iridiumand a specific metal and provided over the interlayer, and a secondlayer containing iridium and provided over the first layer.

[0040] This structure is formed when the baking is performed at arelatively low temperature of 750° C. or lower, for example, and thereis little movement of the iridium.

[0041] The electromechanical transducer in another embodiment of thepresent invention comprises an interlayer formed from a compoundselected from the group consisting of zirconium oxide, tantalum oxide,silicon nitride, and aluminum oxide and formed on the surface where thetransducer is installed, and a bottom electrode formed over theinterlayer. The bottom electrode comprises a first layer containing aspecific metal and provided over the interlayer, and a second layercontaining iridium and provided over the first layer.

[0042] This structure is formed when the baking is performed at arelatively high temperature of over 750° C., for example, and there ismuch movement of the iridium.

[0043] The above-mentioned second layer is characterized in that theiridium that has diffused from the lower layer side is separated fromthe iridium present from the outset. An adhesive layer composed of ametal that adheres to both the interlayer and the bottom electrode mayalso be formed between these layers.

[0044] For example, it can be checked that the volumetric ratio in thebottom electrode accounted for by the alloy containing iridium is atleast 2/5 and no more than 4/5. The “alloy containing iridium” refers toan alloy of iridium and titanium, oxygen, or the like.

[0045] The ink jet printer of the present invention is characterized inthat the electromechanical transducer of the present invention isprovided as an actuator over the diaphragm film that serves as theinstallation surface. The ink jet printer is also characterized bycomprising this ink jet recording head as a printing means.

[0046] The method of the present invention for manufacturing anelectromechanical transducer comprises the steps of using a compoundselected from the group consisting of zirconium oxide, tantalum oxide,silicon nitride, and aluminum oxide to form an interlayer on the surfacewhere this transducer is installed, forming a bottom electrode over thisinterlayer, forming a ferroelectric thin film precursor over this bottomelectrode, and baking.

[0047] Here, the step of forming the bottom electrode comprises thesteps of using iridium to form a first iridium layer, using a specificmetal to form a metal layer over the first iridium layer, and usingiridium to form a second iridium layer over the metal layer, the bakingstep being a step of forming the ferroelectric thin film precursor andthen baking it at a temperature of 750° C. or lower, thereby diffusingthe iridium of the first iridium layer and converting the first iridiumlayer and the metal layer into an alloy layer in which iridium isalloyed with the metal.

[0048] The method for manufacturing an electromechanical transducer inanother embodiment of the present invention comprises the steps of usinga compound selected from the group consisting of zirconium oxide,tantalum oxide, silicon nitride, and aluminum oxide to form aninterlayer on the surface where this transducer is installed, forming abottom electrode over the interlayer, forming a ferroelectric thin filmprecursor over the bottom electrode, and baking.

[0049] Here, the step of forming the bottom electrode comprises thesteps of using iridium to form a first iridium layer, using a specificmetal to form a metal layer over the first iridium layer, and usingiridium to form a second iridium layer over the metal layer.

[0050] The baking step is a step of forming the ferroelectric thin filmprecursor and then baking it at a temperature higher than 750° C.,thereby diffusing the iridium of the first iridium layer and moving theiridium of the first iridium layer to the second iridium layer.

[0051] Preferably, the ratio of the thickness of the first iridium layerprior to baking to the thickness of the bottom electrode overall is setto be between 1/3 and 4/5. The reason for this is that stress will bemoderated more efficiently if the thickness of the iridium layer iswithin this range.

[0052] The method of the present invention for manufacturing anelectromechanical transducer may further comprise the step of using ametal that will adhere to the layers above and below to form an adhesivelayer between the bottom electrode and the interlayer.

[0053] Here, the step of forming a bottom electrode is a step of forminga film such that the following relationship is satisfied:

dT=3.6×d ₀+2.4×d ₁+0.8×d ₂+2.3×d ₃

[0054] when we let d₀ be the thickness of said adhesive layer prior tobaking, d₁ be the thickness of said first iridium layer, d₂ be thethickness of said metal layer, d₃ be the thickness of said secondiridium layer, and dT be the thickness of said bottom electrode overallafter baking. The reason for this is that the thickness of the layerafter crystallization varies as indicated by the above relationship as aresult of baking after formation in this relationship.

BRIEF DESCRIPTION OF THE DRAWINGS

[0055]FIG. 1 is a structural diagram of an ink jet printer;

[0056]FIG. 2 is an exploded oblique view of an ink jet recording head;

[0057]FIG. 3 is cross sectional diagrams of the main steps formanufacturing an ink jet recording head;

[0058]FIG. 4 is a graph of the degree of (111) and (100) orientation ofa PZT film when the titanium film thickness is varied;

[0059]FIG. 5 is a graph of the piezoelectric constant d₃₁ of a PZT filmwhen the titanium film thickness is varied;

[0060]FIG. 6 is a graph of the distribution of the constituent elementsin the film thickness direction of an electromechanical transducer;

[0061]FIG. 7 is a graph of the distribution of the constituent elementsin the film thickness direction of an electromechanical transducer;

[0062]FIG. 8 is cross sectional diagrams of the steps for manufacturingan FRAM memory cell;

[0063]FIG. 9 is a cross sectional diagram of an electromechanicaltransducer;

[0064]FIG. 10 is cross sectional diagrams of the steps for manufacturingan electromechanical transducer;

[0065]FIG. 11 is cross sectional diagrams of the main steps formanufacturing an ink jet recording head;

[0066]FIG. 12 is a drawing of a cross sectional TEM photograph of an inkjet recording head;

[0067]FIG. 13 is a compositional analysis graph for the adhesive layerafter heat treatment;

[0068]FIG. 14 is a compositional analysis graph for the bottom electrodeafter heat treatment;

[0069]FIG. 15 is a compositional analysis graph for the adhesive layerafter heat treatment;

[0070]FIG. 16 is a cross sectional diagram of an electromechanicaltransducer;

[0071]FIG. 17 is cross sectional diagrams of the steps for manufacturingan electromechanical transducer;

[0072]FIG. 18 is a cross sectional diagram of an electromechanicaltransducer;

[0073]FIG. 19 is a cross sectional diagram of the step for manufacturingan electromechanical transducer;

[0074]FIG. 20 is a measurement graph illustrating the relationship ofthe piezoelectric constant and the thickness of the first iridium layerwith respect to the overall thickness of the bottom electrode prior tobaking in an embodiment of baking at 700° C.;

[0075]FIG. 21 is a measurement graph illustrating the relationship ofthe piezoelectric constant and the volumetric ratio of the bottomelectrode after baking accounted for by the alloying containing iridiumin an embodiment of baking at 700° C.;

[0076]FIG. 22 is a measurement graph illustrating the relationship ofthe piezoelectric constant and the thickness of the first iridium layerwith respect to the overall thickness of the bottom electrode prior tobaking in an embodiment of baking at 850° C.; and

[0077]FIG. 23 is a measurement graph illustrating the relationship ofthe piezoelectric constant and the volumetric ratio of the bottomelectrode after baking accounted for by the alloying containing iridiumin an embodiment of baking at 850° C.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] Embodiment 1 of the Invention

[0079] This embodiment pertains to a technique in which a ferroelectricthin film device is utilized as an ink discharge drive source(electromechanical transducer) for an ink jet recording head. Thisembodiment will be described through reference to FIGS. 1 to 7.

[0080]FIG. 1 is a structural diagram of an ink jet printer. The ink jetprinter chiefly comprises an ink jet recording head 100, a main unit102, a tray 103, and a head drive mechanism 106. The ink jet recordinghead 100 is equipped with ink jet cartridges 101 of four colors: yellow,magenta, cyan, and black, which make full-color printing possible. Thisink jet printer is also internally equipped with a dedicated controllerport or the like, which controls the timing of ink discharge from theink jet recording head 100 and the scanning of the head drive mechanism106, and affords high-precision ink control, half-tone processing, andso on. The main unit 102 is equipped with the tray 103 at its rear, andwith an automatic sheet feeder (automatic continuous paper feedmechanism) 105 internally, which automatically feeds out recording paper107, with this recording paper 107 being discharged from a dischargeslot 104 at the front. The recording paper 107 can be ordinary paper,special paper, recommended OHP sheets, glossy paper, glossy film, levelsheets, standard-size postcards, or the like.

[0081] Next, FIG. 2 is an exploded oblique view of an ink jet recordinghead. The type shown here has a common channel for the ink provided oninside of the pressure chamber substrate. As shown in this figure, theink jet recording head is constituted by a pressure chamber substrate 1,a nozzle plate 2, and a base 3. On the pressure chamber substrate 1, asilicon monocrystalline substrate is etched, after which are separatedfrom one another. A plurality of slender pressure chambers 10 areprovided to the pressure chamber substrate 1, and a common channel 12for supplying ink to all of the pressure chambers (cavities) 10 isprovided. Side walls 11 are erected between the pressure chambers 10 tokeep them apart. Electromechanical transducers are attached as inkdischarge drive sources to the base 3 of the pressure chamber substrate1. These electromechanical transducers are ferroelectric thin filmdevices manufactured according to the method of the present invention,and are devices for converting electrical energy into mechanical energy.These transducers are also called piezoelectric actuators ormicro-displacement control devices. The wiring from the variouselectromechanical transducers is bundled on a wiring board 4 which is aflexible cable, and is controlled by a print engine component.

[0082] The nozzle plate 2 is laid over the pressure chamber substrate 1.Nozzles (discharge ports) 21 for discharging ink droplets are formed atlocations corresponding to the pressure chambers 10 in the nozzle plate2. The nozzles 21 are arranged in rows that are more or less parallel tothe main scanning direction of the ink jet recording head duringprinting, and the pitch between the nozzles is suitably set according tothe printing precision. For instance, if the resolution is set at1440×720 dpi, the nozzle diameter will be extremely fine, andhigh-precision printing with ultra-fine ink dots will be possible. Thenumber of nozzles of each color is determined according to the colorprinting precision; for instance, there can be 32 black nozzles and 32nozzles of each color. The base 3 is molded from plastic or the like,and serves as an attachment stand for the pressure chamber substrate 1.

[0083]FIG. 3F is a cross sectional diagram of the main components of theink jet recording head. The pressure chamber 10 is formed by etching inthe pressure chamber substrate 1. The electromechanical transducer 13 isformed on top of the pressure chamber 10 via a diaphragm film 5 and asurface preparation layer 6. The mechanical displacement of theelectromechanical transducer 13 changes the internal volume of thepressure chamber 10 and discharges the ink contained in the pressurechamber 10 from the nozzle 21. The purpose of the surface preparationlayer 6 is to prepare the surface for the formation of theelectromechanical transducer 13, and plays A particularly important rolein the orientation of the ferroelectric thin film of the presentinvention. The role of the surface preparation layer 6 will be discussedin more detail below. The electromechanical transducer 13 comprises abottom electrode 71, a titanium layer 8, a ferroelectric thin film 9,and an top electrode 72. The ferroelectric thin film 9 is subjected to a(111) priority orientation treatment for the (111) plane or the (100)plane by the manufacturing method of the present invention.

[0084] A ferroelectric having at least titanium and lead as itsconstituent components is preferable as the type of the ferroelectricthin film 9. Favorable examples include lead titanate (PbTiO₃), leadtitanate zirconate (Pb(Zr,Ti)O₃), lead lanthanum titanate((Pb,La),TiO₃), lead lanthanum titanate zirconate ((Pb,La)(Zr,Ti)O₃),and lead zirconium-titanate magnesium-niobate (Pb′(Zr,Ti)(Mg,Nb)O₃).Lead titanate zirconate (PZT) is particularly favorable.

[0085] The bottom electrode 71 either consists of a single layer ofiridium film, or has a laminated structure comprising an (iridiumlayer)/(platinum layer), a (platinum layer)/(iridium layer), or an(iridium layer)/(platinum layer)/(iridium layer), in that order startingat the surface preparation layer 6. An alloy of iridium and platinum isalso acceptable. The lattice constant of the ferroelectric thin film 9can be matched by increasing or decreasing the iridium and platinumproportional contents. There are no particular restrictions on the topelectrode 72 as long as it is a conductive material that can be used asan ordinary electrode, but examples include Pt, RuO₂, IrO₂, and othersingle-layer films, or Pt/Ti, Pt/Ti/TiN, Pt/TiN/Pt, Ti/Pt/Ti,TiN/Pt/TiN, Pt/Ti/TiN/Ti, RuO₂/TiN, IrO₂/Ir, IrO₂/TiN, and otherlaminated films of two or more layers. An ultra-thin titanium thin film,a chromium thin film, or another suitable buffer layer may be interposedbetween the surface preparation layer 6 and the bottom electrode 71 inorder to increase the adhesive strength therebetween. It is alsopossible to use a structure in which the diaphragm film 5 is omitted andthe surface preparation layer 6 doubles as a diaphragm film. Also, whilenot shown in the figure, a passivation film can be used to cover theelectromechanical transducer 13 and the entire surface preparation layer6 that is exposed on the surface. A fluororesin, silicon oxide film,epoxy resin, and the like are favorable as this passivation film.

[0086] Working Example

[0087] The steps for manufacturing the electromechanical transducer inthis embodiment will now be described, along with the main steps formanufacturing an ink jet recording head, through reference to FIG. 3.First, as shown in FIG. 3A, a diaphragm film 5 and a surface preparationlayer 6 were formed on a pressure chamber substrate 1. A siliconemonocrystalline substrate with a diameter of 100 mm and a thickness of220 μm was used, for example, as the pressure chamber substrate 1. Forthe diaphragm film 5, dry oxygen was allowed to flow into a 1100° C.furnace to conduct thermal oxidation for about 22 hours, forming athermal oxidation film with a thickness of approximately 1 μm.Alternatively, a film may be formed by suitably choosing anotherformation method such as CVD. The diaphragm film 5 is not limited to asilicon dioxide film, and may instead be a zirconium oxide film, atantalum oxide film, a silicon nitride film, or an aluminum oxide film.Next, in order to form a film of zirconium oxide (ZrO₂) as the surfacepreparation layer 6, a film was formed in a thickness of about 400 nm byreactive sputtering involving the introduction of oxygen gas and usingzirconium as the target. Other film formation methods may be usedinstead, such as forming a film by RF sputtering with a zirconium oxidetarget, or forming a film of zirconium by DC sputtering and thensubjecting this film to thermal oxidation.

[0088] Next, a bottom electrode 71 was formed over the surfacepreparation layer 6 (FIG. 3B). This bottom electrode 71 had a laminatestructure comprising platinum/iridium (starting from the surfacepreparation layer 6 side), with each film being about 100 nm thick.Alternatively, the laminate structure may comprise iridium/platinum oriridium/platinum/iridium (from the surface preparation layer 6 side), ora film may be formed by sputtering using iridium alone as the target. Inthe step of heat treating the ferroelectric thin film discussed below,part of the iridium is oxidized, forming an iridium oxide layer betweencolumnar crystals of platinum. This iridium oxide prevents the oxygenfrom escaping from the ferroelectric thin film, and thereby prevents thecharacteristics of the ferroelectric thin film from deteriorating.

[0089] A titanium layer 8 was then laminated over the bottom electrode71 (FIG. 3C). DC magnetron sputtering was utilized to form the titaniumlayer 8, with the thickness ranging between 2 and 10 nm. The reason forkeeping the thickness within this range will be discussed below. CVD,vapor deposition, or another such film formation process can also beused to form the titanium layer 8.

[0090] Next, a ferroelectric thin film 9 and top electrode 72 wereformed over the titanium layer 8 (FIG. 3D). In this embodiment, a PZTfilm was formed by sol-gel method as the ferroelectric thin film 9. Asol-gel method generally involves subjecting an organometal compoundsuch as a metal alkoxide to hydrolysis in a solution system, conductingpolycondensation to grow metal-oxygen-metal bonds, and finally bakingthis to complete the production of an inorganic oxide. An advantage of asol-gel method is that it yields a uniform film at a low substratetemperature. Furthermore, adhesion to the substrate is excellent becausethe film is formed from a solution. In particular, with the presentinvention, when the ferroelectric thin film is formed by sol-gel method,crystallization will proceed successively from the bottom electrode sidetoward the top electrode side, so control of orientation is superior. Inspecific terms, the substrate is coated with a solution containing anorganometal compound, and the coating is dried and then baked. Examplesof organometal compounds that can be used include metal methoxides,ethoxides, propoxides, butoxides, and other such alkoxides thatconstitute an inorganic oxide, and acetate compounds. Nitrates,oxalates, perchlorates, and other such inorganic salts may also be used.To produce an inorganic oxide from these compounds, it is necessary topromote hydrolysis and polycondensation reactions, and therefore watermust be added to the coating solution. The amount added will vary withthe system, but if too large, the reaction will proceed too quickly andthe resulting film will tend to be uneven, and it will also be difficultto control the reaction velocity. The reaction will also be difficult tocontrol if the amount of added water is too small, so the proper amountshould be used. The reaction velocity and reaction form can becontrolled by adding a hydrolysis acceleration catalyst, or a chelatingagent coordinated to the metal atoms. Common acids and bases can be usedas hydrolysis acceleration catalysts. The film quality will be greatlyaffected by the type of catalyst. Examples of chelating agents includeacetylacetone, ethyl acetoacetate, and diethyl malonate. The solventshould be one in which the above-mentioned materials will notprecipitate, that is, one with excellent miscibility. The solutionconcentration will vary with the coating method, but in the case of spincoating, the solution viscosity should be adjusted to between a fewcentipoise and a few dozen centipoise. Removal of organic matter andcrystallization will be promoted by baking the film coating. The bakingtemperature will vary with the material, but can be lower than that usedin the baking of ordinary metal oxide powders.

[0091] In this embodiment, a mixed solution of Pb(CH₃COO)₂.3H₂O,Zr(t-OCH₄H₉)₄, and Ti(i-OC₃H₇)₄ was readied as the starting raw materialfor the PZT film. This mixed solution was applied by spin coating at1500 rpm in a thickness of 0.1 μm, and degreasing was performed at atemperature of 400° C. This step was repeated five times, which yieldeda gel with a film thickness of 0.5 μm. Finally, crystallization waseffected by RTA (Rapid Thermal Annealing). This treatment was conductedfor 5 minutes at 650° C. The ferroelectric thin film 9 was obtained in athickness of 0.5 μm through this process. When a ferroelectric thin filmdevice is used as an electromechanical transducer, the ferroelectricthin film is also called a piezoelectric film. Next, a film of platinumwas formed by DC sputtering in a thickness of 100 nm as the topelectrode 72 over the ferroelectric thin film 9.

[0092] Next, the top electrode 72 was spin-coated with a resist, andthis product was exposed and developed at the locations where thepressure chambers were to be formed, thereby producing a pattern. Usingthe remaining resist as a mask, the top electrode 72, ferroelectric thinfilm 9, titanium layer 8, and bottom electrode 71 were etched, and theelectromechanical transducer 13 was separated so as to correspond to theposition where the pressure chamber was to be formed (FIG. 3E). Anetching mask was then applied over the position where the pressurechamber was to be formed, and dry etching was performed using an activegas such as a parallel plate type of reactive ion etching gas, whichetched the pressure chamber substrate 1 down to a predetermined depthand formed the pressure chamber 10 (FIG. 3E). The remaining unetchedportion became the side walls 11. The etching of the pressure chambersubstrate 1 can also be accomplished by wet etching using ahigh-concentration alkali aqueous solution, such as a 5 to 40 wt %potassium hydroxide aqueous solution.

[0093] Finally, as shown in FIG. 3F, a resin or the like was used tojoin the nozzle plate 2 to the pressure chamber substrate 1. The nozzles21 can be formed by making holes at specific locations in the nozzleplate 2 by lithography, laser working, FIB working, discharge working,or the like. In the joining of the nozzle plate 2 to the pressurechamber substrate 1, the nozzles 21 were positioned so that theycorresponded to the spaces of the various pressure chambers 10. The inkjet recording head was completed by attaching the pressure chambersubstrate 1 and the joined nozzle plate 2 to the base 3.

[0094] The inventors measured the degree of orientation (%) of the (100)and (111) planes of the ferroelectric thin film 9 (PZT film) formed bythe above manufacturing process with respect to changes in the thicknessof the titanium layer 8. The measurement results are given in FIG. 4.The degree of orientation of the planes here is defined as theproportional diffraction intensity of the (100) plane, the (110) plane,and the (111) plane when the sum of the diffraction intensities of theseplanes is 100. As shown in the figure, the proportional orientation ofthe (111) plane was 15 to 45% when the thickness of the titanium layer 8was within a range of 2 to 10 nm, but was 45 to 90% within a range of 10to 20 nm. Meanwhile, the proportional orientation of the (100) plane was40 to 90% when the thickness of the titanium layer 8 was within a rangeof 2 to 10 nm, but was 5 to 40% within a range of 10 to 20 nm.

[0095] It can be seen from the above results that when a ferroelectricthin film device is used as an electromechanical transducer, in alow-frequency drive band, the preferred range is one in which the (111)plane is the priority orientation, that is, a range in which thethickness of the titanium layer 8 is 10 to 20 nm. On the other hand, itcan be seen that when this device is used as an electromechanicaltransducer in a high-frequency drive band, or when a ferroelectric thinfilm device is used as a capacitor for a FRAM, DRAM, or other suchmemory device, the preferred range is one in which the (100) plane isthe priority orientation, that is, a range in which the thickness of thetitanium layer 8 is 2 to 10 nm.

[0096] Applications of the present invention are not, however, limitedto those given above, and a suitable orientation should be chosenaccording to the frequency that will be used. For example, when anelectromechanical transducer is used as an ink jet recording head, the{100} priority orientation probably should be about 70% and the {111}priority orientation about 30% with a drive frequency band of about 14kHz or 28 kHz (high frequency band). Here, the degree of orientation isexpressed as I(XYZ)/{I(100)+I(110)+I(111)} when we let I(XYZ) expressthe reflection intensity of the planar orientation (XYZ) plane of theferroelectric thin film as measured by wide-angle XRD.

[0097] The inventors further measured the change in the piezoelectricconstant d₃₁ of the ferroelectric thin film 9 (PZT film) with respect tochanges in the thickness of the titanium layer 8. The measurement wasconducted using DC drive, the results of which are given in FIG. 5. Asshown in this figure, when the thickness of the titanium layer 8 wasbetween 2 and 10 nm, the piezoelectric constant d₃₁ was 170 pC/N to 200N, and when the thickness of the titanium layer 8 was between 10 and 20nm, the piezoelectric constant d₃₁ was 200 pC/N to 220 pC/N. It wasconfirmed from the above results that when an electromechanicaltransducer is driven by DC, the piezoelectric characteristics will besuperior when the thickness of the titanium layer 8 is 10 to 20 nm.

[0098] The inventors also measured by SIMS analysis the distribution ofthe various component elements in the thickness direction of theelectromechanical transducer 13 manufactured by the above manufacturingprocess. The measurement results are given in FIGS. 6 and 7. FIG. 6 isthe measurement results when the thickness of the titanium layer 8 was10 nm, and FIG. 7 is the measurement results when the thickness of thetitanium layer 8 was 20 nm. The horizontal axis denotes time, but sincethe electromechanical transducer 13 was measured in the depth directionby SIMS analysis, this axis actually denotes the various layers in thefilm thickness direction, namely, the PZT film (ferroelectric thin film9)/BE (bottom electrode 71)/ZrO₂ (surface preparation layer 6)/SiO₂(diaphragm film 5). The titanium layer 8 is at the interface between thePZT film and the bottom electrode. The vertical axis denotes the amountsof element distribution. As can be seen from these figures, thedistribution of titanium (Ti) is nearly average in the film thicknessdirection within the PZT film, with the distribution amount increasingin the vicinity of the bottom electrode. It seems that the titaniumlayer 8 laminated over the bottom electrode 71 serves as a nucleus forthe crystallization of the PZT film, promoting crystallization.

[0099] The reason is not clear why the ferroelectric thin film 9 has a(111) priority orientation if the thickness of the titanium layer 8 is10 to 20 nm. The inventors conducted experiments into this, but theyhave yet to discover a film with which the above-mentioned effect can beobtained on any surface preparation layer other than a zirconium oxidefilm. It therefore seems likely that a zirconium oxide film has somekind of effect in terms of controlling the orientation of aferroelectric thin film. Nor could they obtain the above-mentionedeffect with elements other than titanium, such as the other elementsthat constitute a ferroelectric, including lead and zirconium. They haveyet to find a film having the same function as the titanium layer 8. Onthe other hand, they confirmed that the (111) priority orientation and(100) priority orientation can be controlled by setting the thickness ofthe titanium layer 8 to within the above-mentioned range, regardless ofthe thickness of the ferroelectric thin film 9 or that of the topelectrode 72.

[0100] The inventors have also confirmed that the above-mentioned effectcan be obtained in an MOD (Metal Organic Decomposition) process. Theywere unable, however, to obtain this effect with other film formationmethods besides a sol-gel method, although they attempted to control theorientation of a PZT film by sputtering, laser ablation, and CVD.Whereas the crystallization of a PZT film gradually proceeds from thebottom electrode side toward the top electrode side with a sol-gel orMOD process, the crystallization of the PZT film proceeds at random withCVE, sputtering, and so on, and the resulting lack of regularity incrystallization seems to be one likely cause of the difficulty incontrolling orientation.

[0101] The orientation of a PZT film can be controlled with thisembodiment without any special manufacturing equipment being required.Furthermore, the only difference from a conventional process formanufacturing an electromechanical transducer is the addition of alamination process for the surface preparation layer and the titaniumlayer, so the orientation of a PZT film can be controlled by a simplemeans.

[0102] Embodiment 2 of the Invention

[0103] A ferroelectric thin film has an extremely large dielectricconstant, ranging from a few hundred to a few thousand, and when usedfor the insulating film of a capacitor, the resulting capacitor has asmall surface area and large capacity that are favorable for circuits oflarge-scale integration. A ferroelectric thin film has spontaneouspolarization, and because the polarization direction can be inverted bythe action of an external electrical field, this characteristic can beutilized to manufacture a nonvolatile memory. An FRAM in which aferroelectric thin film such as this is used as the capacitor insulatingfilm has numerous advantages over a conventional nonvolatile memory,such as better nonvolatility, higher operating speed, lower energyconsumption, and more rewrites.

[0104] This embodiment pertains to a technique in which a ferroelectricthin film device is utilized as a capacitor for an FRAM memory cell. Inspecific terms, a film of zirconium oxide is formed as the surfacepreparation layer of the capacitor, and a bottom electrode, titaniumthin film, ferroelectric thin film, and top electrode are formed in thatorder over this film. As discussed above, the ferroelectric thin filmcan be set to a (100) priority orientation and a film that is favorableas a capacitor insulating film can be obtained by setting the thicknessof the titanium thin film to about 2 to 10 nm. The steps formanufacturing a FRAM memory cell will now be described through referenceto FIG. 8.

[0105] Working Example

[0106] As shown in FIG. 8A, a nitride film (Si₃N₄) was formed over theentire surface of a silicon substrate 101, after which holes were madeby photoetching in that portion of the nitride film where the activeregion was to be formed. The exposed portion of the silicon substrate101 was oxidized by wet oxidation using steam, thereby forming a LOCOS(LOCal Oxidation of Silicon) 102. The unnecessary nitride film was thenremoved, after which a gate oxidation film with a thickness of 150 Å wasformed by HCl oxidation. Polycrystalline silicon was deposited on thesubstrate surface by the pyrolysis of monosilane (SiH₄), and phosphorus(P) was ion-implanted at a concentration of about 10²¹/cm³. After this,this polycrystalline silicon was worked as shown in FIG. 8A byphotoetching and by dry etching using CF₄ gas or the like, therebyforming a gate electrode 103. The gate electrode 103 was then masked andarsenic (As) was ion-implanted, forming a source region 104 and a drainregion 105 through self-alignment. Further, phosphate glass wasdeposited by CVD, forming an interlayer insulating film 106.

[0107] Then, as shown in FIG. 8B, the surface preparation layer 6,bottom electrode 71, titanium layer 8, ferroelectric thin film 9, andtop electrode 72 were formed in that order over the interlayerinsulating film 106. Zirconium oxide was formed by sputtering in athickness of 200 nm as the surface preparation layer 6, and a laminatestructure of platinum/iridium in a film thickness of 100 nm each wasformed as the bottom electrode 71. The titanium layer 8 was then formedin a thickness of 2 to 10 nm by DC sputtering over the bottom electrode71. Further, a PZT film was formed by sol-gel method in a thickness of0.2 μm as the ferroelectric thin film 9. This ferroelectric thin film 9functions as a capacitor insulating film.

[0108] Next, as shown in FIG. 8C, the laminate structure comprising thetop electrode 72, the ferroelectric thin film 9, the titanium layer 8,the bottom electrode 71, and the surface preparation layer 6 was etchedby ion milling, thereby forming a capacitor 107 over the gate electrode103 via the interlayer insulating film 106. Phosphate glass wasdeposited by plasma CVD of tetraethyl orthosilicate (TEOS) as aninterlayer insulating film 108, and contact holes communicating with thetop electrode 72 and the drain region 105 were made, after whichaluminum wiring 109 was formed by DC sputtering, photoprocessing, and analuminum etching process. The source region 104 of the FRAM memory cellobtained by the above manufacturing process was connected to a bit line,and the gate electrode 103 was connected to a word line. The topelectrode 72 was connected to a drive line.

[0109] The orientation of a capacitor insulating film can be controlledwith this embodiment without any special manufacturing equipment beingrequired. Furthermore, the only difference from a conventional processfor manufacturing an FRAM memory cell is the addition of a laminationprocess for the surface preparation layer and the titanium layer, so theorientation of a capacitor insulating film can be controlled by a simplemeans.

[0110] Embodiment 3 of the Invention

[0111] This embodiment pertains to a technique for manufacturing aferroelectric thin film device in which iridium alone is used for thebottom electrode. With this embodiment, a bottom electrode composed ofiridium alone is formed over a surface preparation layer composed ofzirconium oxide. A titanium layer (titanium nucleus), which is theelement that constitutes the ferroelectric thin film (piezoelectricfilm), is then laminated over the bottom electrode, and the thickness ofthe titanium layer is adjusted to about 15 to 30 nm, which prevents theadmixture of oxygen into the bottom electrode during the baking of theferroelectric thin film in a sol-gel method.

[0112] Working Example

[0113] The steps for manufacturing the electromechanical transducer aremore or less the same as the electromechanical transducer manufacturingsteps described in Embodiment 1, and the following description willfocus on the differences.

[0114] First, as shown in FIG. 3A, a diaphragm film 5 composed of asilicon dioxide film was formed in a thickness of 1 μm over the surfaceof a pressure chamber substrate 1 with a thickness of 220 μm, over whicha surface preparation layer 6 composed of a zirconium oxide film waslaminated in a thickness of 400 nm. Then, in order to enhance theadhesion between the surface preparation layer 6 and the bottomelectrode 71, an adhesive layer (not shown in the figure) composed oftitanium was formed in a thickness of about 10 nm over the surfacepreparation layer 6.

[0115] A bottom electrode 71 was then formed from iridium alone bysputtering in a thickness of about 200 nm (FIG. 3B), after which atitanium layer 8 was formed in a thickness of 20 nm (FIG. 3C). Then, asshown in FIGS. 3D, E, and F, a ferroelectric thin film 9 was formed bysol-gel method, a top electrode 72 was formed by sputtering, and thelaminate structure of these thin films was then etched, which separatedthe electromechanical transducers according to the pressure chambers.The pressure chamber substrate 1 was etched to form the pressurechambers 10, and the nozzle plate 2 was joined.

[0116] Table 1 shows the various characteristics of an electromechanicaltransducer obtained by the above manufacturing process (present example)and an electromechanical transducer obtained by conventionalmanufacturing process (conventional example). In both cases, thethickness of the surface preparation layer 6 is 400 nm, the thickness ofthe adhesive layer is 10 nm, and the thickness of the bottom electrode71 (iridium electrode) is 200 nm. The thickness of the ferroelectricthin film 9 of the electromechanical transducer in the present exampleis 20 nm, while the thickness of the titanium layer 8 of theelectromechanical transducer in the conventional example is 5 nm. TABLE1 Present example Conventional example PZT crystal orientation mixtureof (111) plane mixture of (111) plane and (110) plane and (110) planeThickness of bottom 210 nm 440 nm electrode after baking Piezoelectricconstant 142 pC/N 145 pC/N Young's modulus of 300 Gpa 250 Gpa bottomelectrode Breakage rate during 0% 7% head drive

[0117] Based on the above results, the thickness of the bottom electrode71 more than doubled in the conventional example, whereas the thicknessof the bottom electrode 71 only increased to 10 nm in the presentexample. The cause of this seems to be that oxygen is taken into thebottom electrode 71 in the step of baking the ferroelectric thin film 9in the conventional example, which increases the thickness of the bottomelectrode 71, whereas in the present example the oxygen content in thebottom electrode 71 is suppressed by the titanium layer 8 formed in athickness of 20 nm over the bottom electrode 71. Similar results werealso obtained when the thickness of the titanium layer 8 formed over thebottom electrode 71 was between 15 and 30 nm. In addition to the sol-gelmethod, the ferroelectric thin film 9 can also be formed by MOD process.

[0118] The bottom electrode 71 becomes hard and brittle if it containsoxygen, so the electromechanical transducer may break when used as anactuator. As can be seen from the breakage rate for theelectromechanical transducers during head drive, which is given in theabove table, the rate was 7% in the conventional example, whereas it was0% in the present example. It was also confirmed that the Young'smodulus of the bottom electrode was higher in the present example.

[0119] Due to the effect of the titanium layer 8 laminated over thebottom electrode 71, the ferroelectric thin film 9 was a mixture of(111) plane orientation and (110) plane orientation, which differs fromthe mixture of (111) plane orientation and (100) plane orientationobtained with the conventional manufacturing method.

[0120] With the embodiment described above, the oxygen content in thebottom electrode can be minimized during the baking of the ferroelectricthin film by sol-gel method or MOD process by laminating a titaniumlayer in a thickness of 15 to 30 nm over a bottom electrode composed ofiridium alone, which means that the bottom electrode will exhibit bettertoughness, and an actuator with superior reliability can be realized.

[0121] Embodiment 4 of the Invention

[0122] This embodiment relates to the bottom electrode of anelectromechanical transducer with which adhesion to the installationsurface can be enhanced without compromising the piezoelectriccharacteristics.

[0123]FIG. 9 is a cross sectional diagram illustrating the layerstructure when the electromechanical transducer pertaining to thisembodiment is formed over an installation surface. As shown in thefigure, an electromechanical transducer 40 is produced by the successivelamination of an adhesive layer 41, a bottom electrode 42, ananti-diffusion layer 43, a ferroelectric thin film (piezoelectric film)44, and a top electrode 45 over the installation surface. There are noparticular restrictions on the installation surface, but in thisembodiment it corresponds to the diaphragm of an ink jet recording head(for instance, a silicon oxide film or a laminate structure of a siliconoxide film layer and a zirconium oxide film).

[0124] The adhesive layer 41 is manufactured by the method of thepresent invention for manufacturing an electromechanical transducer, andis formed from an alloy containing an anti-diffusion metal. Thisanti-diffusion metal is selected, for example, from the group consistingof iridium (Ir), palladium (Pd), rhodium (Rh), ruthenium (Ru), andosmium (Os). A characteristic of these metals is that they prevent themovement of metals such as titanium and chromium, which are readilydiffused by heat, along the grain boundaries of the crystal grains ofthe above metals. The main component of the adhesive layer 41 is analloy of the above-mentioned anti-diffusion metal and the metal thatconstitutes the bottom electrode. Because platinum is used for thebottom electrode in this embodiment, the adhesive layer is an alloy ofplatinum and the above-mentioned anti-diffusion metal. However, a smallamount of the adhesive metal formed at the outset, such as titanium orchromium, remains at the location of this adhesive layer. Specifically,this adhesive layer 41 is not a layer whose composition stays constantfrom when it is first formed, and is instead a layer produced as aresult of the movement of elements occurring in the course of the heattreatment step. The thickness of the adhesive layer 41 is equal to thecombined thickness of the adhesive metal layer applied prior to the heattreatment and the first anti-diffusion metal layer.

[0125] The bottom electrode 42 is one of the electrodes used to applyvoltage to the ferroelectric thin film 44, and is formed from aconductive material, such as platinum (Pt), in a thickness of about 0.4μm. With a conventional product, the thickness had to be over 0.5 μmbecause of the movement of the adhesive metal through this bottomelectrode, but with this embodiment the anti-diffusion metal plays thisrole, so the film can be 0.2 μm thinner than in the past. The topelectrode 45 is the other electrode for applying voltage to theferroelectric thin film 44, and is formed from a conductive material,such as platinum (Pt), in a thickness of about 0.1 μm.

[0126] The anti-diffusion layer 43 is formed from an alloy of ananti-diffusion metal and an adhesive metal. The anti-diffusion metal isthe same as above, and is selected, for example, from the groupconsisting of iridium, palladium, rhodium, ruthenium, and osmium. Theadhesive metal is formed as an adhesive metal layer prior to heattreatment, and is either titanium or chromium, for example. Theanti-diffusion layer 43 is a layer in which a second anti-diffusionmetal layer formed from an anti-diffusion metal prior to heat treatmentis alloyed with the adhesive metal that has come through from theadhesive metal layer, and thereby forms crystals. The function of thesecond anti-diffusion metal layer, which is the forerunner to thisanti-diffusion layer 43, is to prevent the adhesive metal from diffusinginto the ferroelectric thin film 44 during the heat treatment step, andto prevent the lead or oxygen present in the ferroelectric thin film 44from escaping into the bottom electrode 42 during the heat treatmentstep. The anti-diffusion layer 43 is thus formed by the movement ofelements, so the thickness thereof varies according to the amounts inwhich the second anti-diffusion metal layer and the adhesive metal layerare formed prior to the heat treatment. For instance, there will beminute fluctuations depending on the size of the crystal grains composedof an alloy of anti-diffusion metal and adhesive metal.

[0127] The ferroelectric thin film 44 consists of crystals of anordinary piezoelectric ceramic. Favorable examples include aferroelectric piezoelectric material such as lead titanate-zirconate(PZT), or the product of adding to this a metal oxide such as magnesiumoxide or nickel oxide, or niobic acid. The composition of theferroelectric thin film 44 is suitably selected after taking intoaccount the characteristics and intended application of theelectromechanical transducer. In specific terms, it is possible to uselead titanate (PbTiO₃), lead titanate zirconate (Pb(Zr,Ti)O₃), leadzirconate (PbZrO₃), lead lanthanum titanate ((Pb,La),TiO₃), leadlanthanum titanate zirconate ((Pb,La)(Zr,Ti)O₃), lead zirconium-titanatemagnesium-niobate (Pb′(Zr,Ti)(Mg,Nb)O₃), or the like. A film withsuperior piezoelectric characteristics can be obtained by suitableaddition of niobium (Nb) to lead titanate or lead zirconate.

[0128] The ferroelectric thin film should be thin enough that cracks donot form during the manufacturing process, but should be thick enoughthat it will exhibit sufficient displacement characteristics. Inparticular, because this embodiment involves a structure with which theadhesive metal will not diffuse into the ferroelectric thin film evenafter a heat treatment has been conducted numerous times, it is possiblefor the film to be made thicker than conventional products by numerousheat treatments. In the past, adhesion was diminished by diffusion ofthe adhesive metal if the baking was carried out more than twice, butwith this embodiment, there is no loss of adhesion even after bakingfour or more times. Accordingly, the thickness of the ferroelectric thinfilm 44 can be 1 μm or more, for example.

[0129] Working Example

[0130] Next, a method for manufacturing an ink jet recording head,including the method of the present invention for manufacturing anelectromechanical transducer, will be described through reference toFIGS. 10 and 11. First, a diaphragm film 5 was formed on the surface ofa pressure chamber substrate 1 composed of a silicon monocrystallinesubstrate (FIG. 10A). In this step, a high-temperature treatment shouldbe carried out in an oxidative atmosphere containing oxygen or steam bymeans of a commonly used thermal oxidation method or the like to form athermal oxidation film composed of silicon dioxide. The result of thisstep was the formation of the diaphragm film 5 in a suitable thickness(1.0 μm, for instance) over the pressure chamber substrate 1 of aspecific thickness (220 μm, for instance). Instead of a silicon oxidefilm, it is also possible to form a zirconium oxide film, tantalum oxidefilm, silicon nitride film, or aluminum oxide film. The diaphragm mayalso consist of a laminate structure of a silicon oxide film and azirconium oxide film or the like. To produce a laminate structure, forexample, a silicon oxide film is formed as above in a thickness of about1 μm over a silicon monocrystalline substrate, after which a zirconiumlayer is formed by sputtering, vacuum vapor deposition, or another suchmethod. A high-temperature treatment should then be performed in anoxygen atmosphere, and a zirconium oxide film formed in a thickness ofabout 400 nm.

[0131] Next, a layer 50 was formed from an adhesive metal over thediaphragm film 5 (FIG. 10B). The adhesive metal here refers to titaniumor chromium. These metals are readily diffused by heat treatment duringthe subsequent formation of the ferroelectric thin film 44, but afterdiffusion they move to the anti-diffusion layer 43 and eventually remainin the adhesive layer 41, where they serve to bond the bottom electrode42 and the diaphragm film 5 together. Sputtering, vacuum vapordeposition, or another such method may be used to form the adhesivemetal layer 50. The adhesive metal layer 50 should be thick enough toallow an adequate supply of metal for adhesion, but not so thick thatthere will be no diffusion to the ferroelectric thin film. A thicknessof about 20 nm is good.

[0132] Next, a layer 51 of anti-diffusion metal was formed over theadhesive metal layer 50 (FIG. 10C). This layer leaves behind part of theadhesive metal diffused by the subsequent heat treatment, and functionsas the adhesive layer 41 that enhances the adhesive strength between thebottom electrode 42 and the diaphragm film 5. Sputtering, vacuum vapordeposition, or another such method is used to form the firstanti-diffusion metal layer 51. The first anti-diffusion metal layer 51should be thick enough that it will cause part of the adhesive metaldiffused in the direction of the ferroelectric thin film to remainbehind. A thickness of about 20 nm is good, for example.

[0133] Next, a layer 42 of a bottom electrode was formed over the firstanti-diffusion metal layer 51 (FIG. 10D). Sputtering or another suchmethod was used to form the bottom electrode 42. With a conventionalproduct, the film thickness had to be at least 500 nm in order toprevent the diffusion of titanium, but with this embodiment theanti-diffusion metal prevents the diffusion of titanium, so the film canbe formed in a thickness of 400 nm or less.

[0134] Next, a layer 52 of anti-diffusion metal was formed over thebottom electrode 42 (FIG. 10E). This layer functions as a barrier thathalts the diffusion of the adhesive metal that has diffused through thebottom electrode 42 as a result of the subsequent heat treatment.Sputtering, vacuum vapor deposition, or another such method may be usedto form the second anti-diffusion metal layer 52. The secondanti-diffusion metal layer 52 should be thick enough to halt thediffusion of the adhesive metal into the ferroelectric thin film, and afilm thickness of about 20 nm is good, for example. It is preferable forthe adhesive metal layer, the first anti-diffusion metal layer, thebottom electrode, and the second anti-diffusion metal layer to be formedcontinuously in a vacuum in order to prevent contamination.

[0135] Next, the ferroelectric thin film 44 was formed by lamination ofa ferroelectric thin film by sol-gel method (FIG. 10F to FIG. 11H). Theadhesive metal layer 50 was diffused all the way to the secondanti-diffusion metal layer 52, and the anti-diffusion layer 43 producedat the location of this second anti-diffusion metal layer 52, by thebaking treatment performed for the crystallization of the ferroelectricthin film. This step also involves promoting the alloying of the firstanti-diffusion metal layer 51 with the bottom electrode 42, and therebyproducing the adhesive layer 41 at the location of the adhesive metallayer 50 and the first anti-diffusion metal layer 51.

[0136] First, a sol composed of an organometal alkoxide was applied byspin coating or another coating method over the bottom electrode 42.This coating was then dried for a specific length of time at a specifictemperature to evaporate the solvent. After drying, degreasing wasperformed for a specific time at a specific high temperature in an airatmosphere, and the organic ligands coordinated to the metal werepyrolyzed, which yielded a metal oxide. These steps of coating, drying,and degreasing were repeated a specific number of times (such as four ormore) to laminate four or more layers of ferroelectric thin filmprecursor 441 to 44 n (n is the number of coatings) (FIG. 10F→FIG.11G→FIG. 10F→FIG. 11G . . . ). As a result of this drying anddegreasing, the metal alkoxide and acetate in the solution formed anetwork of metal-oxygen-metal via the pyrolysis of ligands. After theferroelectric thin film precursors had been laminated a specific numberof times, a baking treatment was performed in a specific atmosphere.This baking treatment formed a perovskite crystal structure havinganything from an amorphous gel structure to any kind of crystalstructure.

[0137] In the course of the above-mentioned heat treatment, the titaniumin the adhesive metal layer 50 diffuses along the grain boundaries ofthe crystals. Part of this diffusion is prevented by the firstanti-diffusion metal layer 51. Meanwhile, the platinum of the bottomelectrode 42 diffuses somewhat toward this first anti-diffusion metallayer 51. As a result, an alloy layer consisting of the diffused metal,the metal that makes up the bottom electrode, and the adhesive metal isformed at the location of the first anti-diffusion metal layer 51 andthe adhesive metal layer 50. This is the adhesive layer 41 (FIG. 11H).

[0138] The titanium in the adhesive metal layer 50 passes through thebottom electrode 42 and reaches the second anti-diffusion metal layer52, where this diffusion is stopped. Accordingly, an alloy layer of theanti-diffusion metal and the adhesive metal is formed at the location ofthe second anti-diffusion metal layer 52. This is the anti-diffusionlayer 43 (FIG. 11H).

[0139] Next, the top electrode 45 was formed by electron beam vapordeposition, sputtering, or another such method over the ferroelectricthin film 44 (FIG. 11I). Platinum, iridium, or the like was used for thematerial of the top electrode, and the thickness was about 100 nm.

[0140] The basic form of the electromechanical transducer is complete atthe above step. This electromechanical transducer can be made to operateas the piezoelectric device of the present invention if it is etchedinto a shape suited to the place where it is to be used and if it ismanufactured such that voltage can be applied between the top and bottomelectrodes. With this embodiment, the laminate structure of theabove-mentioned piezoelectric device was etched to match the ink jetrecording head, and the ink jet recording head was then manufactured bythe steps described below. FIG. 11 illustrates the cross sectionalstructure of three electromechanical transducers in particular, but inactual practice the number and spacing of the electromechanicaltransducers may be varied according to the resolution of the ink jetrecording head.

[0141] First, after the formation of the laminate structure of thevarious electromechanical transducers, the top electrode 45, theferroelectric thin film 44, the anti-diffusion layer 43, the bottomelectrode 42, and the adhesive layer 41 were masked in a shape matchingthe pressure chambers 10, and etching was performed around this mask(FIG. 11J). In specific terms, first a resist material was applied overthe top electrode in a uniform thickness by spinner method, spraying, oranother such method, a mask was formed in the shape of theelectromechanical transducers, and then exposure and developing wereperformed to form a resist pattern over the top electrode 45. Thisproduct was subjected to ordinary ion milling, dry etching, or anothersuch process to etch away the top electrode 45, ferroelectric thin film44, anti-diffusion layer 43, bottom electrode 42, and adhesive layer 41and shape the electromechanical transducers 40.

[0142] Next, the pressure chambers 10 were formed by etching the otherside of the pressure chamber substrate 1 from that on which theelectromechanical transducers 40 were formed (FIG. 11J). For example,the spaces for the pressure chambers 10 were etched into the siliconsubstrate by anisotropic etching, parallel plate type of reactive ionetching, or another form of anisotropic etching using an active gas. Theunetched portion that remains behind becomes the side walls 11.

[0143] Finally, the nozzle plate 2 is bonded to the etched pressurechamber substrate 1 with an adhesive agent to manufacture the maincomponents of an ink jet recording head (FIG. 11K). When the parts arebonded together, the nozzles 21 are aligned so that they will bearranged in the spaces of the various pressure chambers 10. The pressurechamber substrate 1 with its bonded nozzle plate 2 is attached to ahousing to complete an ink jet recording head 1. Instead of the nozzleplate 2 being bonded, the nozzle plate 2 and the pressure chambersubstrate 1 may be formed by integral etching. There is no need for thebonding step when the nozzle plate and the pressure chamber substrateare manufactured at the same time by integral etching. The nozzles aremade at positions corresponding to the pressure chambers 10.

[0144] In the above manufacturing method, the electromechanicaltransducers were formed using titanium as the adhesive metal, platinumas the bottom electrode, iridium as the anti-diffusion metal, andPZT-PMN as the ferroelectric thin film. FIG. 12 is a drawing of a crosssectional TEM (Transmission Electron Microscopy) photograph of thecrystal structure thereof. As this figure confirms, an adhesive layerhas been formed in which alloying has proceeded between the diaphragmfilm and the bottom electrode. It also confirms the formation of ananti-diffusion layer which is an alloy layer of anti-diffusion metalcrystals and adhesive metal at the interface between the bottomelectrode and the ferroelectric thin film.

[0145]FIG. 13 is a compositional analysis graph for the adhesive layer.This figure relates to the composition of that region of the adhesivelayer relatively near the bottom electrode. As can be seen from thefigure, with this embodiment only a tiny amount of titanium (arrow 1),which is the composition of the adhesive metal layer that had beenformed at this location prior to heat treatment, remains. Instead,platinum (Pt; arrow 2), which is the metal that makes up the bottomelectrode, and iridium (Ir; arrow 3), which is the anti-diffusion metalthat had made up the anti-diffusion metal layer prior to heat treatment,are present. It can be confirmed that the two metals have been alloyed.The heat treatment causes the titanium to diffuse, and the platinum inthe bottom electrode and the iridium in the anti-diffusion metal layermove in and form an adhesive layer.

[0146]FIG. 14 is a compositional analysis graph for the bottomelectrode. As can be seen from the figure, the platinum (Pt; arrow 1)present from the outset accounts for virtually all of the composition.Part of the titanium (Ti; arrow 2) that is the adhesive metal that hasdiffused from the adhesive metal layer remains.

[0147]FIG. 15 is a compositional analysis graph for the adhesive layer.As shown in this figure, the iridium (Ir; arrow 1) that is theanti-diffusion metal that had been formed in the anti-diffusion metallayer prior to heat treatment is present. Also beginning to appear isthe titanium (Ti; arrow 2) that is the adhesive metal that has diffusedfrom the adhesive metal layer. Also present is the oxygen (O; arrow 3)that has moved from the ferroelectric thin film. The composition here isa mixture of almost completely unoxidized iridium and titanium oxide.Specifically, it can be seen that the anti-diffusion layer prevents thetitanium from moving to the ferroelectric thin film, and prevents theoxygen from escaping from the ferroelectric thin film to the bottomelectrode.

[0148] Table 2 shows the change in adhesion when the composition of theanti-diffusion layer and adhesive layer was varied. In the comparativeexamples, there is no layer corresponding to the anti-diffusion layer,and the adhesive layer consists of titanium. TABLE 2 BottomFerroelectric Adhesive Electrode electrode thin film Number of strengthconstitution thickness thickness bakings (mN) Compar. Example 500 nm 0.8μm 2 17.8 Working Example 500 nm 0.8 μm 2 18.0 Compar. Example 500 nm1.2 μm 4 14.2 Working Example 500 nm 1.2 μm 4 18.8 Compar. Example 300nm 1.2 μm 4 9.8 Working Example 300 nm 1.2 μm 4 19.8

[0149] As can be seen from Table 2, adhesion was better in the workingexamples than the comparative examples. In particular, there was arelative increase in adhesion when the number of bakings was increasedand the thickness of the ferroelectric thin film was over 1 μm.Therefore, the layer structure of this embodiment is also effective whenthe ferroelectric thin film thickness is increased to over 1 μm.

[0150] Next, Table 3 shows the breakdown voltage and piezoelectricconstant d₃₁ of an electromechanical transducer in working examples andcomparative examples of the above-mentioned layer structure when thethickness of the bottom electrode was 500 nm and the thickness of theferroelectric thin film was varied. TABLE 3 Ferroelectric Break-Piezoelectric Piezoelectric Electrode thin film down constant atconstant at constitution thickness voltage 15 V (pC/V) 25 V (pC/V)Compar. Example 0.8 μm 41 V 178 161 Working Example 0.8 μm 60 V 196 175Compar. Example 1.2 μm 62 V 191 170 Working Example 1.2 μm 93 V 240 195

[0151] As can be seen from Table 3, the breakdown voltage andpiezoelectric constant d₃₁ are higher in the working examples than thecomparative examples. The reason for this is that no low-dielectricconstant layer is present at the interface between the bottom electrodeand the ferroelectric thin film in the electromechanical transducers ofthe working examples. The reason the value of the piezoelectric constantd₃₁ varies with the measured voltage is that, because the appliedelectrical field intensity is high with an electromechanical transducer,there is a tendency for the piezoelectric constant d₃₁ to decrease asthe electrical field increases in intensity. Thus, increasing thethickness of the ferroelectric thin film is an effective way to enhancethe characteristics of an electromechanical transducer. Making theferroelectric thin film too thick, however, is undesirable because thedisplacement efficiency will decrease. For example, a ferroelectric thinfilm thickness that is favorable for a high-resolution ink jet recordinghead is probably about 1 or 2 μm.

[0152] Embodiment 5 of the Invention

[0153] This embodiment relates to an electromechanical transducer formedat a relatively low temperature, to a method for manufacturing thiselectromechanical transducer, and to an ink jet recording head and inkjet printer that make use of the same.

[0154]FIG. 16 is a cross sectional diagram of a layer structure, inwhich the electromechanical transducer portion of an ink jet recordinghead in this embodiment has been enlarged.

[0155] As shown in this figure, an electromechanical transducer 80comprises an interlayer 92, an adhesive layer 81, a bottom electrode 82,a ferroelectric thin film (piezoelectric film) 83, and a top electrode84, all laminated over an oxide film 91 that forms the installationsurface.

[0156] The interlayer 92 is an elastic layer, and together with theoxide film 91, constitutes a diaphragm film 70. The interlayer 92 isformed from a compound selected from the group consisting of zirconiumoxide, tantalum oxide, silicon nitride, and aluminum oxide. Here, it isformed from zirconium oxide. The interlayer 92 is thick enough tofunction as an elastic layer (for example, a thickness between 200 and800 nm).

[0157] The adhesive layer 81 is formed between the interlayer 92 and thebottom electrode 82, from a metal that adheres to these two layers. Thisadhesive layer serves to improve the adhesion of the electromechanicaltransducer to the installation surface, but it need not be formed whengood adhesion can be ensured. Titanium and chromium are examples ofmetals with good adhesion. The adhesive layer 81 should be thick enoughto ensure the minimum acceptable adhesion, such as 10 nm or more.

[0158] The bottom electrode 82 consists of a first layer 824 and asecond layer 825. The first layer 824 and second layer 825 are formed asa result of the movement of the composition resulting from themanufacturing method of this embodiment, as discussed below.

[0159] The first layer 824 is a layer composed of an alloy of iridiumand a specific metal, provided over the interlayer 92. An example ofthis metal is platinum. This alloy is produced when the iridium (821)provided under the metal layer (822) of platinum or the like is moved byheat to the metal layer and alloyed there. Accordingly, the first layer824 is not uniformly mixed throughout the entire layer, and instead hasa somewhat heterogeneous crystal structure in which iridium crystals areadmixed in the crystallization of the platinum or other metal.

[0160] The second layer 825 is provided over the first layer 824, and isformed as a layer containing iridium. This layer is produced when theiridium layer (823) provided from the outset is crystallized as it is.

[0161] In the bottom electrode 82 consisting of the first layer 824 andthe second layer 825, the volumetric ratio of the bottom electrode 82accounted for by the alloy containing iridium (such as an alloy of thetitanium or other metal that has moved from the adhesive layer 81, theoxygen that has escaped from the ferroelectric thin film 83, andiridium) is at least 2/5 and no more than 4/5.

[0162] The ferroelectric thin film 83 is a ferroelectric consisting ofan ordinary piezoelectric ceramic. Favorable examples include aferroelectric piezoelectric material such as lead titanate-zirconate(PZT), or the product of adding to this a metal oxide such as magnesiumoxide or nickel oxide, or niobic acid. The composition of theferroelectric thin film 83 is suitably selected after taking intoaccount the characteristics and intended application of theelectromechanical transducer. In specific terms, it is possible to uselead titanate (PbTiO₃), lead titanate zirconate (Pb(Zr,Ti)O₃), leadzirconate (PbZrO₃), lead lanthanum titanate ((Pb,La),TiO₃), leadlanthanum titanate zirconate ((Pb,La)(Zr,Ti)O₃), lead zirconium-titanatemagnesium-niobate (Pb′(Zr,Ti)(Mg,Nb)O₃), or the like. A film withsuperior piezoelectric characteristics can be obtained by suitableaddition of niobium (Nb) to lead titanate or lead zirconate.

[0163] The ferroelectric thin film should be thin enough that cracks donot form during the manufacturing process, but should be thick enoughthat it will exhibit sufficient displacement characteristics.

[0164] The top electrode 84 is an electrode paired with the bottomelectrode 82, and is formed from a specific metal such as platinum oriridium. The thickness thereof is about 100 nm.

[0165] Working Example

[0166] An example of manufacturing the electromechanical transducer andink jet recording head of the present invention will now be describedthrough reference to FIGS. 17 and 18.

[0167] First, the oxide film 91 was formed on the surface of thepressure chamber substrate 1 (FIG. 17A). In this step, ahigh-temperature treatment is carried out in an oxidative atmospherecontaining oxygen or steam to form the oxide film 91 composed of silicondioxide. Any thermal oxidation method or CVD that is ordinarily used canbe used in this step as well. The result of this step was the formationof the oxide film 91 in a suitable thickness (1.0 μm, for instance) overthe pressure chamber substrate 1 composed of a silicon monocrystallinesubstrate of a specific thickness (220 μm, for instance).

[0168] Next, the interlayer 92 was formed over the oxide film 91 (FIG.17B). A compound selected from the group consisting of zirconium oxide,tantalum oxide, silicon nitride, and aluminum oxide was used as thematerial for this interlayer. If zirconium oxide is used, for example,first a zirconium layer is formed over the oxide film 91 by sputtering,vacuum vapor deposition, or another such method, and this product istreated at high temperature in an oxygen atmosphere to produce ainterlayer 92 of zirconium oxide. The thickness thereof should be about400 nm.

[0169] Next, the bottom electrode 82 was formed over the diaphragm film70 formed in the above step (FIG. 17C). In this example, the adhesivelayer 81 was further formed from an adhesive metal between theelectromechanical transducer 80 and the diaphragm film 70 in order toprevent these from separating. “Adhesive metal” refers to titanium orchromium. Sputtering, vacuum vapor deposition, or the like may be usedto form the film. The adhesive layer 81 should be thick enough for it tofunction sufficiently as an adhesive metal layer, but not so thick thatthere will be no diffusion into the piezoelectric film. A thickness ofabout 10 nm or more is good.

[0170] The step of forming the bottom electrode comprises the steps offorming a first iridium layer 821, forming a metal layer 822, andforming a second iridium layer 823.

[0171] The first iridium layer 821 is formed by causing iridium toadhere by sputtering or another such method. The thickness of the firstiridium layer 821 is important. Specifically, the thickness of the firstiridium layer 821 is set such that the ratio of this thickness to thethickness of the bottom electrode 82 as a whole will be from 1/3 to 4/5.Since not only the thickness of this layer 821, but the thickness of themetal layer 822 and the second iridium layer 823 is also affected, thethickness of each layer is set after the required thickness of thebottom electrode 82 as a whole has been determined. Here, the thicknessis adjusted such that the following relationship is satisfied:

dT=3.6×d ₀+2.4×d ₁+0.8×d ₂+2.3×d ₃  (1)

[0172] when we let d₀ be the thickness of the adhesive layer prior tobaking, d₁ be the thickness of the first iridium layer, d₂ be thethickness of the metal layer, d₃ be the thickness of the second iridiumlayer, and dT be the thickness of the bottom electrode overall afterbaking. This is because the stress moderation that is an object of thepresent invention can be accomplished more effectively when thelamination is in these proportions.

[0173] The metal layer 822 is formed by causing a specific conductivemetal, such as platinum, to adhere by sputtering or another such method.There are no particular restrictions on the thickness thereof, but about100 nm is good, for example.

[0174] The second iridium layer 823 is formed by again causing iridiumto adhere over the metal layer 822 by sputtering or another such method.The second iridium layer 823 should be thick enough to prevent theiridium, titanium, or other such metal that has diffused through themetal layer 822 from diffusing into the piezoelectric film. 20 nm ormore is good, for example.

[0175] It is preferable for the adhesive layer 81, the first iridiumlayer 821, the metal layer 822, and the second iridium layer 823 to beformed continuously in a vacuum in order to prevent contamination.

[0176] Next, the ferroelectric thin film 83 was formed by lamination ofa ferroelectric thin film by sol-gel method (FIGS. 17D and E). First, asol composed of an organometal alkoxide was applied by spin coating oranother coating method over the bottom electrode 82. This coating wasthen dried for a specific length of time at a specific temperature toevaporate the solvent. After drying, degreasing was performed for aspecific time at a specific high temperature in an air atmosphere, andthe organic ligands coordinated to the metal were pyrolyzed, whichyielded a metal oxide. These steps of coating, drying, and degreasingwere repeated a specific number of times (such as four or more) tolaminate four or more layers of ferroelectric thin film precursor. As aresult of this drying and degreasing, the metal alkoxide and acetate inthe solution formed a network of metal-oxygen-metal via the pyrolysis ofligands (FIG. 17D).

[0177] The ferroelectric thin film precursors were then baked andcrystallized at a temperature of 750° C. or lower (FIG. 17 E). This heattreatment diffused the iridium of the first iridium layer 821, andconverted the first iridium layer 821 and the metal layer 822 into afirst layer 824 that was an alloy layer in which iridium and platinumwere alloyed.

[0178] This heat treatment also resulted in the ferroelectric thin filmprecursors forming a perovskite crystal structure from their amorphousform they had when they were precursors, and changed them into a thinfilm that exhibited an electromechanical transducing action.

[0179] Finally, the top electrode 84 was formed over the ferroelectricthin film 83 by electron beam vapor deposition, sputtering, or anothersuch method (FIG. 17F). Platinum, iridium, or the like may be used forthe material of the top electrode, and the thickness is about 100 nm.

[0180] The basic form of the electromechanical transducer is complete atthe above step. This electromechanical transducer can be made to operateas the piezoelectric device of the present invention if it is etchedinto a shape suited to the place where it is to be used and if it ismanufactured such that voltage can be applied between the top and bottomelectrodes. Thereafter, an ink jet recording head is completed byseparating the electromechanical transducer by etching into transducerscorresponding to the pressure chambers according to the stepsillustrated in FIGS. 11J to L, and working the pressure chambersubstrate.

[0181] With this embodiment, an electrode is sandwiched by an iridiumlayer over an interlayer, and baked at a temperature of 750° C. orlower, which effectively moderates the residual stress in the bottomelectrode through the diffusion of the iridium, and makes it possible toprovide an electromechanical transducer having good piezoelectriccharacteristics, and products to which this electromechanical transduceris applied.

[0182] Embodiment 6 of the Invention

[0183] This embodiment relates to the structure of an electromechanicaltransducer manufactured when baking is performed at a temperature over750° C. in the manufacturing process of Embodiment 5.

[0184]FIG. 18 is a cross sectional diagram of the structure of a layerstructure, in which the electromechanical transducer portion of an inkjet recording head in this embodiment has been enlarged.

[0185] As shown in this figure, an electromechanical transducer 90comprises an interlayer 92, an adhesive layer 81, a bottom electrode 85,a ferroelectric thin film (piezoelectric film) 83, and a top electrode84, all laminated over an oxide film 91 that forms the installationsurface.

[0186] The interlayer 92, adhesive layer 81, ferroelectric thin film 83,and top electrode 84 are the same as in Embodiment 5, and therefore willnot be described in detail.

[0187] The bottom electrode 85 consists of a first layer 826 and asecond layer 827. The first layer 826 and second layer 827 are formed asa result of the movement of the composition resulting from themanufacturing method of this embodiment, as discussed below.

[0188] The first layer 826 is a layer composed of a specific metalprovided over the interlayer 92. This layer is the layered structureresulting after the iridium (821) provided under the metal layer (822)prior to baking has been diffused by heat to the metal layer and passedtherethrough. Accordingly, the first layer 826 consists almost entirelyof metal originally present, such as platinum, but crystals of theiridium that has passed through may remain behind.

[0189] The second layer 827 is provided over the first layer 826, and isformed as a layer containing iridium. This layer is produced by theseparate crystallization of iridium layers comprising a second iridiumlayer (823) provided from the outset and a first iridium layer (821)that has moved in via the metal layer (822).

[0190] In the bottom electrode 85 consisting of the first layer 826 andthe second layer 827, the volumetric ratio of the bottom electrode 85accounted for by the alloy containing iridium (such as an alloy of thetitanium or other metal that has moved from the adhesive layer 81, theoxygen that has escaped from the ferroelectric thin film 83, andiridium) is at least 2/5 and no more than 4/5.

[0191] Working Example

[0192] An example of manufacturing an electromechanical transducer willnow be described through reference to FIG. 19. The baking step in thismanufacturing method is different from that described for FIG. 17. Therest of the steps, such as the oxide film formation step (FIG. 19A, theinterlayer formation step (FIG. 19B), the bottom electrode formationstep (FIG. 19C), the ferroelectric thin film formation step (FIGS. 19Dand E), and the top electrode formation step (FIG. 19F), are the same asin Embodiment 5 given above.

[0193] The baking step of this example is characterized in that thebaking is performed at a temperature higher than 750° C. Baking at thisrelatively high temperature causes the iridium of the first iridiumlayer 821 to diffuse, and causes this iridium to pass through the metallayer 822 and move almost completely into the second iridium layer 823.

[0194] Also, this heat treatment results in the ferroelectric thin filmprecursors forming a perovskite crystal structure from their amorphousform they had when they were precursors, and changes them into a thinfilm that exhibited an electromechanical transducing action.

[0195] After the formation of the various layers of theelectromechanical transducer, the step of forming the ink jet recordinghead and the structure of the printer in which this is utilized are thesame as in Embodiment 5.

[0196] With this embodiment, an electrode is sandwiched by an iridiumlayer over an interlayer, and baked at a temperature higher than 750°C., which effectively moderates the residual stress in the bottomelectrode through the diffusion of the iridium, and makes it possible toprovide an electromechanical transducer having good piezoelectriccharacteristics, and products to which this electromechanical transduceris applied.

[0197] The inventors manufactured several electromechanical transducersby the above method, using zirconium oxide for the interlayer 92,titanium for the adhesive layer 81, and platinum for the metal layer822. The transducer manufactured by the method of Embodiment 5 with thebaking temperature set at 700° C. is termed working Example 1, while thetransducer manufactured by the method of Embodiment 6 with the bakingtemperature set at 850° C. is termed Working Example 2.

[0198]FIG. 20 shows the results of measuring the relationship betweenthe piezoelectric constant d₃₁ and the ratio of the thickness of thefirst iridium layer to the thickness of the overall bottom electrodeprior to baking in the electromechanical transducer of WorkingExample 1. FIG. 21 shows the results of measuring the relationshipbetween the piezoelectric constant d₃₁ and the volumetric ratio of thebottom electrode accounted for by the alloy containing iridium afterbaking in the electromechanical transducer of Working Example 1.

[0199] The piezoelectric constant before the pressure chambers wereformed and the residual stress released was 150 pC/N in each case.Forming the pressure chambers tends to moderate the stress and lower thepiezoelectric constant. The lower is this proportional decrease, thebetter are the characteristics.

[0200] As can be seen from FIGS. 20 and 22, it was confirmed thatregardless of the baking temperature, a piezoelectric device thatexhibited good piezoelectric characteristics was obtained when thethickness ratio of the first iridium layer to the bottome electrodeprior to baking was from about 1/3 to about 4/5.

[0201] As can be seen from FIGS. 21 and 23, it was confirmed thatregardless of the baking temperature, a piezoelectric device thatexhibited good piezoelectric characteristics was obtained when thevolumetric ratio of the bottom electrode accounted for by the alloycontaining iridium after baking was at least 2/5 and no more than 4/5.The reason this volumetric ratio should not exceed 4/5 is that if thisratio is too high, the bottom electrode will consist almost entirely ofiridium, and the device will be too hard and brittle to be used as anactuator for an ink jet recording head.

[0202] The relationship between the thickness of the adhesive layer, thefirst iridium layer, the metal layer, and the second iridium layer priorto baking, and the thickness of the overall bottom electrode afterbaking was confirmed to satisfy the relation of Formula 1 in bothworking examples.

[0203] The present invention is not limited to the embodiments givenabove, and can be applied with various modifications thereto. Forinstance, the ferroelectric thin film device manufactured with thepresent invention can be used in the manufacture not only of the inkdischarge drive source of an ink jet recording head, but also anonvolatile semiconductor memory device, a thin film capacitor, apyroelectric detector, a sensor, a surface acoustic wave opticalwaveguide, an optical recording device, a space light modulator, afrequency doubler for a diode laser, and other such ferroelectricdevices, dielectric devices, pyroelectric devices, piezoelectricdevices, and electro-optical devices.

[0204] The present invention allows the orientation of a ferroelectricthin film to be controlled according to the intended application of aferroelectric thin film device. In particular, the orientation of aferroelectric thin film can be controlled merely by adjusting thethickness of the titanium layer, so there is no need for specialequipment, and orientation can be controlled by a simple method.

[0205] The present invention also provides a method for manufacturing anelectromechanical transducer with highly reliable drive characteristics,with which the amount of oxygen contained in a bottom electrode composedof iridium alone can be minimized during the baking of a ferroelectricthin film.

[0206] The present invention also comprises an adhesive layer and ananti-diffusion layer, so even if the bottom electrode is made thinnerthan in a conventional product, the adhesive metal will not becomeadmixed in the piezoelectric film and form a low-dielectric constantlayer, and the oxygen and lead in the ferroelectric thin film will notescape from the bottom electrode into the adhesive layer, so there is nodeterioration in piezoelectric characteristics. Also, because the bottomelectrode can be made thinner, there is greater freedom in choosing thematerial and thickness of the diaphragm film in an effort to optimizethe displacement characteristics. Furthermore, reliability is enhancedbecause good adhesion can be maintained even if the ferroelectric thinfilm is made thinner.

[0207] Finally, the present invention provides an electromechanicaltransducer, and products to which this electromechanical transducer isapplied, with higher reliability because residual stress is moderatedthrough the movement of iridium during baking.

What is claimed is:
 1. A method for manufacturing a ferroelectric thinfilm device, comprising the steps of: forming a bottom electrode filmcontaining at least iridium on a surface preparation layer whose maincomponent is zirconium oxide; laminating an ultra-thin titanium layerover said bottom electrode; and forming a crystallized ferroelectricthin film by forming an amorphous layer containing elemental metal andelemental oxygen that constitute a ferroelectric over said titaniumlayer, and heat treating said amorphous layer, wherein the orientationof said ferroelectric thin film is controlled by adjusting the filmthickness in the lamination of said titanium layer.
 2. The method formanufacturing a ferroelectric thin film device defined in claim 1,wherein the priority orientation of said ferroelectric thin film is setto (100) by keeping the film thickness to at least 2 nm and less than 10nm in the lamination of said titanium layer.
 3. The method formanufacturing a ferroelectric thin film device defined in claim 1,wherein the priority orientation of said ferroelectric thin film is setto (111) by keeping the film thickness to at least 10 nm and less than20 nm in the lamination of said titanium layer.
 4. The method formanufacturing a ferroelectric thin film device defined in any of claims1 to 3, wherein the step of forming said ferroelectric thin film is astep of forming a film by sol-gel method from a ferroelectric whoseconstituent components are at least titanium and lead.
 5. The method formanufacturing a ferroelectric thin film device defined in claim 4,wherein said ferroelectric is lead titanate zirconate.
 6. The method formanufacturing a ferroelectric thin film device defined in any of claims1 to 5, wherein the step of forming said ferroelectric thin film is astep of forming a single layer of an iridium film, or using platinum andiridium to form a laminate film comprising an (iridium layer)/(platinumlayer), a (platinum layer)/(iridium layer), or an (iridiumlayer)/(platinum layer)/(iridium layer), in that order starting at saidsurface preparation layer.
 7. The electromechanical transducer, obtainedby the method according to claim 2 or
 3. 8. An ink jet recording head,comprising: the electromechanical transducer defined in claim 7; apressure chamber whose internal volume is varied by the mechanicaldisplacement of said electromechanical transducer; and discharge outletsthat communicate with said pressure chamber and from which ink dropletsare discharged.
 9. The ink jet recording head according to claim 8,wherein said discharge outlets are arranged in rows that are more orless parallel to the main scanning direction.
 10. An ink jet printerwhose printing mechanism is equipped with the ink jet recording headaccording to claim 8 or
 9. 11. A method for manufacturing an ink jetrecording head, comprising the steps of: forming a surface preparationlayer whose main component is zirconium oxide on a silicon substratesurface, either directly or via a diaphragm film; forming a bottomelectrode containing at least iridium over said surface preparationlayer; laminating a titanium layer whose film thickness is at least 10nm and less than 20 nm over said bottom electrode; forming aferroelectric thin film having a priority orientation of (111) byforming an amorphous film containing the elemental metal and elementaloxygen that constitute the ferroelectric over said titanium layer andthen heat treating said amorphous film; manufacturing anelectromechanical conversion device by forming an top electrode oversaid ferroelectric thin film; and separating the electromechanicaltransducer so as to line up with the position where the mechanicaldisplacement of the electromechanical transducer can be imparted to thepressure chamber.
 12. A method for manufacturing an ink jet recordinghead, comprising the steps of: forming a surface preparation layer whosemain component is zirconium oxide over a silicon substrate surface,either directly or via a diaphragm film; forming a bottom electrodecontaining at least iridium over said surface preparation layer;laminating a titanium layer with a thickness of at least 2 nm and lessthan 10 nm over said bottom electrode; forming a ferroelectric thin filmhaving a priority orientation of (100) by forming an amorphous layercontaining elemental metal and elemental oxygen that constitute aferroelectric over said titanium layer, and heat treating said amorphouslayer; manufacturing an electromechanical transducer by forming an topelectrode over said ferroelectric thin film; and separating theelectromechanical transducer so as to line up with the position wherethe mechanical displacement of the electromechanical transducer can beimparted to the pressure chamber.
 13. The method for manufacturing anink jet recording head according to claim 11 or 12, wherein the step offorming said ferroelectric thin film is a step of forming a film bysol-gel method from a ferroelectric whose constituent components are atleast titanium and lead.
 14. The method for manufacturing aferroelectric thin film device defined in claim 13, wherein saidferroelectric is lead titanate zirconate.
 15. The method formanufacturing an ink jet recording head defined in any of claims 11 to14, wherein the step of forming said bottom electrode is a step offorming a single layer of an iridium film, or using platinum and iridiumto form a laminate film comprising an (iridium layer)/(platinum layer),a (platinum layer)/(iridium layer), or an (iridium layer)/(platinumlayer)/(iridium layer), in that order starting at said surfacepreparation layer.
 16. A nonvolatile ferroelectric memory device inwhich a ferroelectric thin film manufactured by the method according toclaim 2 or 3 serves as a capacitor.
 17. A method for manufacturing anonvolatile ferroelectric memory device, comprising the steps of:forming a bottom electrode containing at least iridium over a surfacepreparation layer whose main component is zirconium oxide; laminating atitanium layer whose film thickness is at least 2 nm and less than 10 nmover said bottom electrode; and forming a capacitor insulating filmhaving a priority orientation of (100) by forming an amorphous filmcontaining the elemental metal and elemental oxygen that constitute theferroelectric over said titanium layer and then heat treating saidamorphous film.
 18. The method for manufacturing a nonvolatileferroelectric memory device according to claim 17, wherein the step offorming said capacitor insulating film is a step of forming a film bysol-gel method from a ferroelectric whose constituent components are atleast titanium and lead.
 19. The method for manufacturing a nonvolatileferroelectric memory device defined in claim 18, wherein saidferroelectric is lead titanate zirconate.
 20. The method formanufacturing a nonvolatile ferroelectric memory device defined in anyof claims 17 to 19, wherein the step of forming said bottom electrode isa step of forming a single layer of an iridium film, or using platinumand iridium to form a laminate film comprising an (iridiumlayer)/(platinum layer), a (platinum layer)/(iridium layer), or an(iridium layer)/(platinum layer)/(iridium layer), in that order startingat said surface preparation layer.
 21. A method for manufacturing anelectromechanical transducer, comprising the steps of: forming a bottomelectrode containing at least iridium over a surface preparation layerwhose main component is zirconium oxide; laminating a titanium layerwith a thickness of at least 2 nm and less than 10 nm over said bottomelectrode; and forming a ferroelectric thin film having a priorityorientation of (100) by forming an amorphous layer containing elementalmetal and elemental oxygen that constitute a ferroelectric over saidtitanium layer, and heat treating said amorphous layer.
 22. The methodfor manufacturing an electromechanical transducer to claim 21, whereinthe step of forming said ferroelectric thin film is a step of forming afilm by sol-gel method from a ferroelectric whose constituent componentsare at least titanium and lead.
 23. The method for manufacturing anelectromechanical transducer defined in claim 22, wherein saidferroelectric is lead titanate zirconate.
 24. The method formanufacturing an electromechanical transducer defined in any of claims21 to 23, wherein the step of forming said bottom electrode is a step offorming a single layer of an iridium film, or using platinum and iridiumto form a laminate film comprising an (iridium layer)/(platinum layer),a (platinum layer)/(iridium layer), or an (iridium layer)/(platinumlayer)/(iridium layer), in that order starting at said surfacepreparation layer.
 25. A method for manufacturing an electromechanicaltransducer, comprising the steps of: forming a bottom electrode composedof iridium alone over a surface preparation layer whose main componentis zirconium oxide; laminating a titanium layer whose film thickness isat least 15 nm and less than 30 nm over said bottom electrode; andforming a crystallized ferroelectric thin film by forming an amorphousfilm containing the elemental metal and elemental oxygen that constitutethe ferroelectric over said titanium layer and then heat treating saidamorphous film.
 26. A method for manufacturing an electromechanicaltransducer, comprising the steps of: forming a bottom electrode composedof iridium alone over a surface preparation layer whose main componentis zirconium oxide; laminating an ultra-thin titanium layer over saidbottom electrode; and forming a crystallized ferroelectric thin film byforming an amorphous film containing the elemental metal and elementaloxygen that constitute the ferroelectric over said titanium layer andthen heat treating said amorphous film, wherein the priority orientationof the ferroelectric thin film is controlled to the (111) plane or the(110) plane by adjusting the thickness of said titanium layer to atleast 15 nm and less than 30 nm.
 27. The method for manufacturing anelectromechanical transducer according to claim 25 or 26, wherein thestep of forming said ferroelectric thin film is a step of forming a filmby sol-gel method or MOD method.
 28. An electromechanical transducercomprising a ferroelectric thin film sandwiched between an top electrodeand a bottom electrode, said electromechanical transducer comprising anadhesive layer formed from an alloy containing an anti-diffusion metaland formed between said bottom electrode and the surface where saidtransducer is installed; and an anti-diffusion layer formed from analloy containing said anti-diffusion metal and formed between saidbottom electrode and said ferroelectric thin film.
 29. Theelectromechanical transducer according to claim 28, wherein saidanti-diffusion metal is selected from the group consisting of iridium,palladium, rhodium, ruthenium, and osmium.
 30. The electromechanicaltransducer according to claim 28, wherein said adhesive layer is analloy of said anti-diffusion metal and the metal that constitutes saidbottom electrode.
 31. The electromechanical transducer according toclaim 28, wherein said anti-diffusion layer is an alloy of saidanti-diffusion metal and an adhesive metal that is either titanium orchronium.
 32. The electromechanical transducer according to claim 28,wherein said bottom electrode consists of platinum.
 33. Theelectromechanical transducer according to claim 28, wherein saidferroelectric thin film is formed in a thickness of at least 1 μm. 34.An ink jet recording head, wherein the electromechanical transduceraccording to any of claims 28 to 33 is installed on a diaphragm filmformed on at least one side of a pressure chamber filled with ink. 35.The ink jet recording head according to claim 34, wherein said diaphragmfilm is constituted by the lamination of a silicon oxide film and azirconium oxide film.
 36. An ink jet printer, wherein the ink jetrecording head according to either claim 34 or 35 is provided as an inkdischarge means.
 37. A method for manufacturing an electromechanicaltransducer comprising a ferroelectric thin film sandwiched between antop electrode and a bottom electrode, comprising the steps of: formingan adhesive metal layer composed of an adhesive metal over the surfacewhere said transducer is installed; forming a first anti-diffusion metallayer composed of an anti-diffusion metal over said adhesive metallayer; forming said bottom electrode over said anti-diffusion metallayer; forming a second anti-diffusion metal layer composed of saidanti-diffusion metal over said bottom electrode; and baking saidferroelectric thin film while this ferroelectric thin film is formedover said second anti-diffusion metal layer, and thereby diffusing saidadhesive metal all the way to said second anti-diffusion metal layer andproducing an anti-diffusion layer at the location of said secondanti-diffusion metal layer, promoting the alloying of saidanti-diffusion metal and said bottom electrode, and producing anadhesive layer at the location of said adhesive metal layer and firstanti-diffusion metal layer.
 38. The method for manufacturing aelectromechanical transducer according to claim 37, wherein a metalselected from the group consisting of iridium, palladium, rhodium,ruthenium, and osmium is used as the anti-diffusion metal.
 39. Themethod for manufacturing a electromechanical transducer according toclaim 37, wherein either titanium or chronium is used as said adhesivemetal.
 40. An electromechanical transducer comprising a bottom electrodeand a ferroelectric thin film, comprising: an interlayer formed from acompound selected from the group consisting of zirconium oxide, tantalumoxide, silicon nitride, and aluminum oxide and formed on the surfacewhere said transducer is installed; and a bottom electrode formed oversaid interlayer, said bottom electrode comprising: a first layercomposed of an alloy of iridium and a specific metal and provided oversaid interlayer; and a second layer containing iridium and provided oversaid first layer.
 41. An electromechanical transducer comprising abottom electrode and a ferroelectric thin film, comprising: aninterlayer formed from a compound selected from the group consisting ofzirconium oxide, tantalum oxide, silicon nitride, and aluminum oxide andformed on the surface where said transducer is installed; and a bottomelectrode formed over said interlayer, said bottom electrode comprising:a first layer containing a specific metal and provided over saidinterlayer; and a second layer containing iridium and provided over saidfirst layer.
 42. The electromechanical transducer according to claim 41,wherein said second layer is constituted such that the iridium diffusedfrom the lower layer side during baking is separated from the iridiumpresent since before baking.
 43. The electromechanical transduceraccording to either claim 40 or 41, wherein an adhesive layer comprisinga metal that adheres to said interlayer and said bottom electrode isfurther formed between these two layers.
 44. The electromechanicaltransducer according to claim 43, wherein the volumetric ratio in saidbottom electrode accounted for by the alloy containing iridium is atleast 2/5 and no more than 4/5.
 45. An ink jet recording head, whereinthe electromechanical transducer according to any of claims 40 to 44 isprovided as an actuator over the diaphragm film which is said surfacewhere the transducer is installed.
 46. An ink jet printer, comprisingthe ink jet recording head according to claim 45 as a printing means.47. A method for manufacturing an electromechanical transducercomprising a bottom electrode and a ferroelectric thin film, comprisingthe steps of: using a compound selected from the group consisting ofzirconium oxide, tantalum oxide, silicon nitride, and aluminum oxide toform an interlayer on the surface where said transducer is installed;forming a bottom electrode over said interlayer; forming a ferroelectricthin film precursor over said bottom electrode; and baking, said step offorming the bottom electrode comprising the steps of: using iridium toform a first iridium layer; using a specific metal to form a metal layerover said first iridium layer; and using iridium to form a secondiridium layer over said metal layer, and said baking step being a stepof forming said ferroelectric thin film precursor and then baking it ata temperature of 750° C. or lower, thereby diffusing the iridium of saidfirst iridium layer and converting said first iridium layer and saidmetal layer into an alloy layer in which iridium is alloyed with saidmetal.
 48. A method for manufacturing an electromechanical transducercomprising a bottom electrode and a ferroelectric thin film, comprisingthe steps of: using a compound selected from the group consisting ofzirconium oxide, tantalum oxide, silicon nitride, and aluminum oxide toform an interlayer on the surface where said transducer is installed;forming a bottom electrode over said interlayer; forming a ferroelectricthin film precursor over said bottom electrode; and baking, said step offorming the bottom electrode comprising the steps of: using iridium toform a first iridium layer; using a specific metal to form a metal layerover said first iridium layer; using iridium to form a second iridiumlayer over said metal layer; and forming a ferroelectric thin film oversaid second iridium layer, and said baking step being a step of formingsaid ferroelectric thin film precursor and then baking it at atemperature higher than 750° C., thereby diffusing the iridium of saidfirst iridium layer and moving the iridium of said first iridium layerto said second iridium layer.
 49. The method for manufacturing anelectromechanical transducer according to claim 47 or 48, wherein theratio of the thickness of said first iridium layer prior to baking tothe thickness of said bottom electrode overall is set to be between 1/3and 4/5.
 50. The method for manufacturing an electromechanicaltransducer according to any of claims 47 to 49, further comprising thestep of: using a metal that will adhere to the layers above and below toform an adhesive layer between said bottom electrode and saidinterlayer.
 51. The method for manufacturing an electromechanicaltransducer according to claim 50, wherein said step of forming a bottomelectrode is a step of forming a film such that the followingrelationship is satisfied: dT=3.6×d ₀+2.4×d ₁+0.8×d ₂+2.3×d ₃ when welet d₀ be the thickness of said adhesive layer prior to baking, d₁ bethe thickness of said first iridium layer, d₂ be the thickness of saidmetal layer, d₃ be the thickness of said second iridium layer, and dT bethe thickness of said bottom electrode overall after baking.